Semiconductor memory having both volatile and non-volatile functionality comprising resistive change material and method of operating

ABSTRACT

A semiconductor memory cell including a capacitorless transistor having a floating body configured to store data as charge therein when power is applied to the cell, and a non-volatile memory including a bipolar resistive change element, and methods of operating.

CROSS-REFERENCE

This application claims the benefit of U.S. Provisional Application No.61/546,571, filed Oct. 13, 2011 and titled “A Semiconductor MemoryHaving Both Volatile and Non-Volatile Functionality Comprising ResistiveChange Material and Method of Operating”, which application is herebyincorporated herein, in its entirety, by reference thereto.

This application claims the benefit of U.S. Provisional Application No.61/547,734, filed Oct. 16, 2011 and titled “A Semiconductor MemoryHaving An Electrically Floating Body and Method of Operating”, whichapplication is hereby incorporated herein, in its entirety, by referencethereto.

FIELD OF THE INVENTION

The present invention relates to semiconductor memory technology. Morespecifically, the present invention relates to semiconductor memoryhaving both volatile and non-volatile functionality.

BACKGROUND OF THE INVENTION

Semiconductor memory devices are used extensively to store data. Memorydevices can be characterized according to two general types: volatileand non-volatile. Volatile memory devices such as static random accessmemory (SRAM) and dynamic random access memory (DRAM) lose data that isstored therein when power is not continuously supplied thereto.

Non-volatile memory devices, such as flash erasable programmable readonly memory (Flash EPROM) devices, retain stored data even in theabsence of power supplied thereto. Unfortunately, non-volatile memorydevices typically operate more slowly than volatile memory devices. Forexample, a Flash EPROM device write access time is in the range ofmicroseconds to milliseconds, while the SRAM or DRAM write access timeis in the range of picoseconds to nanoseconds.

Accordingly, it would be desirable to provide a universal type memorydevice that includes the advantages of both volatile and non-volatilememory devices, i.e., fast operation on par with volatile memories,while having the ability to retain stored data when power isdiscontinued to the memory device.

It would further be desirable to provide such a universal type memorydevice having a size that is not prohibitively larger than comparablevolatile or non-volatile devices.

SUMMARY OF THE INVENTION

A purpose of the invention is to provide a semiconductor memory havingboth volatile and non-volatile functionality, which comprises resistivechange material. Examples of resistive change material includes bipolarresistive memory element, such as transition metal oxides,ferroelectric, and ferromagnetic materials.

In at least one embodiment, the memory cell device comprises: asubstrate of first conductivity type; a buried layer at a bottom portionof the substrate, having a second conductivity type; a first regionembedded in the substrate at a first location of the substrate andhaving a second conductivity type; a second region embedded in thesubstrate at a second location the substrate and have the secondconductivity type; a gate positioned in between the first and secondlocations and above a surface of the substrate and insulated from thesurface by an insulating layer; and a resistive change materialdeposited above the region having a second conductivity type.

In one aspect of the present invention, a method of operating a memorycell according to the present invention is provided. In addition,applications of the memory cell, for example as a means to save power inmemory device, are described.

In one aspect of the present invention, a semiconductor memory cell isprovided that includes: a capacitorless transistor having a floatingbody configured to store data as charge therein when power is applied tothe cell; and a non-volatile memory comprising a bipolar resistivechange element.

In at least one embodiment, the bipolar resistive change element isconfigured to store the data stored in the floating body upon transferthereto.

In at least one embodiment, the bipolar resistive change elementcomprises a material selected from at least one of: transition metaloxide materials, ferroelectric materials and ferromagnetic materials.

In at least one embodiment, the bipolar resistive change element iselectrically connected to the capacitorless transistor and a distancebetween the bipolar resistive change element and the capacitorlesstransistor, when electrically connected, is in the range from about 90nm to 1 μm.

In at least one embodiment, the floating body has a first conductivitytype selected from n-type conductivity type and p-type conductivitytype; the memory cell further comprising first and second regions atfirst and second locations of the cell, the first and second regionseach having a second conductivity type selected from n-type conductivitytype and p-type conductivity type and being different from the firstconductivity type; wherein the bipolar resistive change elementcomprises an electrode and a bipolar resistive change materialelectrically connected to one of the first and second regions.

In at least one embodiment, the bipolar resistive change element iselectrically connected to one of the first and second regions via aconductive element.

In at least one embodiment, the cell further includes an addressableline electrically connected to the bipolar resistive change element.

In at least one embodiment, the bipolar resistive change element furthercomprises a conductive material element interconnecting the addressableline and the bipolar resistive change material.

In at least one embodiment, the semiconductor memory cell furtherincludes a substrate being made of a material having a secondconductivity type selected from p-type conductivity type and n-typeconductivity type; a first region having a second conductivity typeselected from p-type and n-type conductivity types, the secondconductivity type being different from the first conductivity type; asecond region having the second conductivity type, the second regionbeing spaced apart from the first region; and a buried layer in thesubstrate below the first and second regions, spaced apart from thefirst and second regions and having the second conductivity type;wherein the floating body is formed between the first and second regionsand the buried layer, the floating body region having the firstconductivity type; and wherein the non-volatile memory is electricallyconnected to one of the first and second regions.

In at least one embodiment, the floating body has a first conductivitytype selected from p-type conductivity type and n-type conductivitytype, the memory cell further comprising: a substrate being made of amaterial having a second conductivity type selected from p-typeconductivity type and n-type conductivity type, the second conductivitytype being different from the first conductivity type; a well in thesubstrate, the well having the first conductivity type; a first regionhaving the second conductivity type; a second region having the secondconductivity type, the second region being spaced apart from the firstregion; and a buried layer located between the well and the first andsecond regions, spaced apart from the first and second regions andhaving the second conductivity type; wherein the floating body is formedbetween the first and second regions and the buried layer; and whereinthe non-volatile memory is electrically connected to one of the firstand second regions.

In at least one embodiment, the substrate is a well formed in a secondsubstrate.

In at least one embodiment, the cell has a three-dimensional structurecomprising a fin structure extending substantially perpendicular to, andabove a top surface of a substrate.

In at least one embodiment, a semiconductor memory array is providedcomprising a plurality of semiconductor memory cell as described above,arranged in a matrix of at least one row and at least one column.

In at least one embodiment, an integrated circuit device is providedthat comprises the semiconductor memory array, as described above, andcircuitry configured to determine whether the semiconductor memoryarray, or a portion of the semiconductor memory array, has been idle fora time period equal to or greater than a predetermined time period.

In at least one embodiment, the floating body comprises a bipolar memorydevice.

In another aspect of the present invention, a semiconductor memory cellis provided that comprises: a silicon controlled rectifier deviceconfigured to store data when power is applied to the cell; and anon-volatile memory comprising a bipolar resistance change element.

In another aspect of the present invention, a method of operatingsemiconductor memory to function as volatile memory, while having theability to retain stored data when power is discontinued to thesemiconductor memory, as provided, the method including: storing data ina capacitorless transistor having a floating body configured to storedata as charge therein when power is applied to the memory, wherein thefloating body operates as a capacitorless DRAM cell or a bi-stable SRAMcell; and storing data in a bipolar resistance change element byconfiguring the bipolar resistance change element in one of a lowresistivity state or a high resistivity state, wherein each of theresistivity states corresponds to a different data value, respectively.

In at least one embodiment, the method further includes restoring thedata from the bipolar non-volatile memory to the floating body asvolatile memory.

In at least one embodiment, the restoring comprises evacuating holesfrom the volatile memory when the bipolar non-volatile memory is in alow resistance state, but maintaining a presently existing charge in thevolatile memory when the bipolar non-volatile memory is in a highresistance state.

In at least one embodiment, the restoring and maintaining are performednon-algorithmically.

In at least one embodiment, the method further includes, after restoringor maintaining data stored in the floating body, resetting the bipolarnon-volatile memory to a predetermined resistivity state.

In at least one embodiment, the bipolar non-volatile memory comprises abipolar resistive change element.

In another aspect of the present invention, a reference cell forcomparing a potential stored in the reference cell to a referencepotential value is provided, the reference cell comprising: a floatingbody having a first conductivity type selected from n-type conductivitytype and p-type conductivity type; a first region having a secondconductivity type selected from the n-type conductivity type and thep-type conductivity type and being different from the first conductivitytype; a second region having the first conductivity type and beingrelatively more heavily doped than the floating body; and a sense lineterminal electrically connected to the second region and configured tobe electrically connected to a structure providing the reference value.

In another aspect of the present invention, a reference cell is providedthat comprises: a memory cell region comprising: a floating body havinga first conductivity type selected from n-type conductivity type andp-type conductivity type; a first region having a second conductivitytype selected from the n-type conductivity type and the p-typeconductivity type and being different from the first conductivity type;and a second region having the second conductivity and being separatedfrom the first region by the floating body; and a reference cell regioncomprising: the floating body; a third region having the firstconductivity type and being separated from the first and second regionsby the floating body; a fourth region having the first conductivity typeand being separated from the first, second and third regions by thefloating body; and being relatively more heavily doped than the floatingbody; and a sense line terminal electrically connected to one or both ofthe third and fourth regions, the sense line terminal being configuredto be electrically connected to a reference value for comparison of thereference value with a potential of the floating body.

In at least one embodiment, the reference cell further comprising asecond sense line terminal connected to the other of the third andfourth regions.

These and other features of the invention will become apparent to thosepersons skilled in the art upon reading the details of the memory cells,arrays, integrated circuits and methods as more fully described below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart illustrating operation of a memory deviceaccording to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a memory cell according to anembodiment of the present invention.

FIG. 3A is a cross-sectional view of a memory cell according to anembodiment of the present invention, showing an embodiment of anon-volatile memory element.

FIG. 3B is a cross-sectional view of a memory cell according to anotherembodiment of the present invention.

FIG. 3C is a top view of a memory cell according to an embodiment of thepresent invention.

FIGS. 4A and 4B schematically illustrate an equivalent circuitrepresentation of the memory cell shown in FIG. 2.

FIG. 5A illustrates an integrated circuit device comprising a memoryarray comprising of a plurality of memory cells shown in FIG. 2.

FIGS. 5B and 5C schematically illustrate multiple cells of the typeshown in FIG. 2 joined to make a memory array.

FIG. 6 schematically illustrates performance of a holding operation on amemory array according to an embodiment of the present invention.

FIG. 7 illustrates exemplary bias conditions applied on the terminals ofa memory cell of the array of FIG. 6.

FIG. 8A shows an energy band diagram characterizing an intrinsic n-p-nbipolar device when a floating body region is positively charged and apositive bias voltage is applied to a buried well region of a memorycell according to an embodiment of the present invention.

FIG. 8B shows an energy band diagram of an intrinsic n-p-n bipolardevice when a floating body region is neutrally charged and a biasvoltage is applied to a buried well region of a memory cell according toan embodiment of the present invention.

FIG. 9A is a schematic view of a memory array showing exemplary biasconditions for performing a read operation on the memory array,according to an embodiment of the present invention.

FIG. 9B shows exemplary bias conditions applied to a selected memorycell during the read operation noted with regard to the array in FIG.9A.

FIG. 10A is a schematic illustration of a memory cell array showingexemplary bias conditions for a write logic-1 operation on the memoryarray through an impact ionization mechanism, according to an embodimentof the present invention.

FIG. 10B illustrates exemplary bias conditions on an exemplary selectedmemory cell from the array of FIG. 10A.

FIG. 11A is a schematic illustration of a memory cell array showingexemplary bias conditions for a write logic-1 operation on the memoryarray through a band-to-band tunneling mechanism, according to anembodiment of the present invention.

FIG. 11B illustrates exemplary bias conditions on an exemplary selectedmemory cell from the array of FIG. 11A.

FIG. 12A is a schematic illustration showing exemplary bias conditionsfor a write logic-0 operation performed on a memory array according toan embodiment of the present invention.

FIG. 12B is a schematic illustration of exemplary bias conditionsapplied to an exemplary selected memory cell from the memory array ofFIG. 12A.

FIG. 13A is a schematic illustration showing exemplary bias conditionsapplied for a bit-selective write logic-0 operation performed on amemory array according to an embodiment of the present invention.

FIG. 13B illustrates exemplary bias conditions applied to the terminalsof an exemplary selected memory cell from the array of FIG. 13A.

FIG. 14 is a schematic illustration showing exemplary bias conditionsapplied for a shadowing operation performed on a memory array accordingto an embodiment of the present invention.

FIG. 15 illustrates exemplary bias conditions applied to the terminalsof an exemplary selected memory cell from the array of FIG. 14.

FIG. 16 is a schematic illustration showing exemplary bias conditionsapplied for a restore operation performed on a memory array according toan embodiment of the present invention.

FIG. 17 illustrates exemplary bias conditions applied to the terminalsof an exemplary selected memory cell from the array of FIG. 16.

FIG. 18 is a schematic illustration showing exemplary bias conditionsapplied for a reset operation performed on a memory array according toan embodiment of the present invention.

FIG. 19 illustrates exemplary bias conditions applied to the terminalsof an exemplary selected memory cell from the array of FIG. 18.

FIG. 20 is a cross-sectional, schematic illustration of a memory cellfabricated on a silicon-on-insulator (SOI) substrate according toanother embodiment of the present invention.

FIGS. 21A and 21B illustrate cross-sectional and top view schematicillustrations of a fin-type memory cell device according to anotherembodiment of the present invention, respectively.

FIG. 22 is a cross-sectional, schematic illustration of a memory cellaccording to another embodiment of the present invention.

FIG. 23 is a cross-sectional view of a memory cell according to anembodiment of the present invention.

FIGS. 24A through 24C schematically illustrate an equivalent circuitrepresentation of the memory cell shown in FIG. 23.

FIG. 25 illustrates an integrated circuit device comprising a memoryarray comprising of a plurality of memory cells shown in FIG. 23.

FIGS. 26A and 26B schematically illustrate multiple cells of the typeshown in FIGS. 24A-24C joined to make a memory array.

FIG. 27 schematically illustrates performance of a holding operation ona memory array according to an embodiment of the present invention.

FIG. 28 illustrates exemplary bias conditions applied on the terminalsof a memory cell of the array of FIG. 27.

FIG. 29 illustrates an algorithm that can be employed to refresh thedata stored in floating body memory cells in parallel, according to anembodiment of the present invention.

FIG. 30 is a schematic, cross-sectional illustration of a memory cellwhich can be used as a reference cell in sensing the state of a floatingbody memory cell according to an embodiment of the present invention.

FIG. 31 is a schematic illustration of a top view of a memory cell whichcan be used as a reference cell in sensing the state of a floating bodymemory cell according to another embodiment of the present invention.

FIGS. 32A and 32B are schematic, cross-sectional illustrations of thecell of FIG. 9 taken along the I-I′ and II-II′ cut lines of FIG. 31,respectively.

FIG. 33 is a schematic view of a memory array showing exemplary biasconditions for performing a read operation on the memory array,according to an embodiment of the present invention.

FIG. 34 shows exemplary bias conditions applied to a selected memorycell during the read operation noted with regard to the array in FIG.33.

FIG. 35 is a schematic illustration of a memory cell array showingexemplary bias conditions for a write logic-1 operation on the memoryarray through an impact ionization mechanism, according to an embodimentof the present invention.

FIG. 36 illustrates exemplary bias conditions on an exemplary selectedmemory cell from the array of FIG. 35.

FIG. 37 is a schematic illustration of a memory cell array showingexemplary bias conditions for a write logic-1 operation on the memoryarray through a band-to-band tunneling mechanism, according to anembodiment of the present invention.

FIG. 38 illustrates exemplary bias conditions on an exemplary selectedmemory cell from the array of FIG. 37.

FIG. 39 is a schematic illustration showing exemplary bias conditionsfor a write logic-0 operation performed on a memory array according toan embodiment of the present invention.

FIG. 40 is a schematic illustration of exemplary bias conditions appliedto an exemplary selected memory cell from the memory array of FIG. 39.

FIG. 41 is a schematic illustration showing exemplary bias conditionsapplied for a bit-selective write logic-0 operation performed on amemory array according to an embodiment of the present invention.

FIG. 42 illustrates exemplary bias conditions applied to the terminalsof an exemplary selected memory cell from the array of FIG. 41.

FIG. 43 is a cross-sectional view of an embodiment of the memory cell ofthe present invention.

FIG. 44A is another cross-sectional view of a memory cell of the presentinvention showing an embodiment of the non-volatile memory element.

FIG. 44B is a top view of a memory cell according to an embodiment ofthe present invention.

FIG. 45 schematically illustrates an equivalent circuit representationof the memory cell shown in FIG. 43.

FIG. 46A illustrates an integrated circuit device comprising a memoryarray comprising of a plurality of memory cells shown in FIG. 43.

FIGS. 46B and 46C schematically illustrate multiple cells of the typeshown in FIG. 43 joined to make a memory array.

FIG. 47 is a schematic illustration showing exemplary bias conditionsapplied for a shadowing operation performed on a memory array accordingto an embodiment of the present invention.

FIG. 48 illustrates exemplary bias conditions applied to the terminalsof an exemplary selected memory cell from the array of FIG. 47.

FIG. 49 is a schematic illustration showing exemplary bias conditionsapplied for a restore operation performed on a memory array according toan embodiment of the present invention.

FIG. 50 illustrates exemplary bias conditions applied to the terminalsof an exemplary selected memory cell from the array of FIG. 49.

FIG. 51 is a schematic illustration showing exemplary bias conditionsapplied for a reset operation performed on a memory array according toan embodiment of the present invention.

FIG. 52 illustrates exemplary bias conditions applied to the terminalsof an exemplary selected memory cell from the array of FIG. 51.

FIG. 53 is a cross-sectional, schematic illustration of a memory cellfabricated on a silicon-on-insulator (SOI) substrate according toanother embodiment of the present invention.

FIGS. 54A and 54B illustrate cross-sectional and top view schematicillustrations of a fin-type memory cell device according to anotherembodiment of the present invention, respectively.

FIG. 55 is a cross-sectional, schematic illustration of a memory cellaccording to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Before the present cells, arrays and methods are described, it is to beunderstood that this invention is not limited to particular embodimentsdescribed, as such may, of course, vary. It is also to be understoodthat the terminology used herein is for the purpose of describingparticular embodiments only, and is not intended to be limiting, sincethe scope of the present invention will be limited only by the appendedclaims.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimits of that range is also specifically disclosed. Each smaller rangebetween any stated value or intervening value in a stated range and anyother stated or intervening value in that stated range is encompassedwithin the invention. The upper and lower limits of these smaller rangesmay independently be included or excluded in the range, and each rangewhere either, neither or both limits are included in the smaller rangesis also encompassed within the invention, subject to any specificallyexcluded limit in the stated range. Where the stated range includes oneor both of the limits, ranges excluding either or both of those includedlimits are also included in the invention.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although any methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of the present invention, the preferred methodsand materials are now described. All publications mentioned herein areincorporated herein by reference to disclose and describe the methodsand/or materials in connection with which the publications are cited.

It must be noted that as used herein and in the appended claims, thesingular forms “a”, “an”, and “the” include plural referents unless thecontext clearly dictates otherwise. Thus, for example, reference to “acell” includes a plurality of such cells and reference to “the array”includes reference to one or more arrays and equivalents thereof knownto those skilled in the art, and so forth.

The publications discussed herein are provided solely for theirdisclosure prior to the filing date of the present application. Nothingherein is to be construed as an admission that the present invention isnot entitled to antedate such publication by virtue of prior invention.Further, the dates of publication provided may be different from theactual publication dates which may need to be independently confirmed.

Definitions

The terms “shadowing” “shadowing operation” and “shadowing process”refer to a process of copying the contents of volatile memory tonon-volatile memory.

“Restore”, “restore operation”, or “restore process”, as used herein,refers to a process of copying the contents of non-volatile memory tovolatile memory.

“Reset”, “reset operation”, or “reset process”, as used herein, refersto a process of setting non-volatile memory to a predetermined state.

DESCRIPTION

FIG. 1 is a flowchart 100 illustrating operation of a memory deviceaccording to the present invention. At event 102, when power is firstapplied to the memory device, the memory device is placed in an initialstate, in a volatile operational mode and the nonvolatile memory is setto a predetermined state. At event 104 the memory device of the presentinvention operates in the same manner as a volatile memory, for exampleas an SRAM or DRAM memory cell. However, during power shutdown, or whenpower is inadvertently lost, or any other event that discontinues orupsets power to the memory device of the present invention, the contentof the volatile memory is loaded into non-volatile memory at event 106,during a process which is referred to here as “shadowing” (event 106),and the data previously held in volatile memory is lost. Shadowing canalso be performed during backup operations, which may be performed atregular intervals during volatile operation 104 periods, and/or at anytime that a user manually instructs a backup.

During a backup operation, the content of the volatile memory is copiedto the non-volatile memory while power is maintained to the volatilememory so that the content of the volatile memory also remains involatile memory. Alternatively, because the volatile memory operationconsumes more power than the non-volatile storage of the contents of thevolatile memory, the device can be configured to perform the shadowingprocess anytime the device has been idle for at least a predeterminedperiod of time, thereby transferring the contents of the volatile memoryinto non-volatile memory and conserving power. As one example, thepredetermined time period can be about thirty seconds, but of course,the invention is not limited to this time period, as the device could beprogrammed with virtually any predetermined time period.

After the content of the volatile memory has been moved during ashadowing operation to nonvolatile memory, the shutdown of the memorydevice occurs, as power is no longer supplied to the volatile memory. Atthis time, the memory device retains the stored data in the nonvolatilememory. Upon restoring power at event 108, the content of thenonvolatile memory is restored by transferring the content of thenon-volatile memory to the volatile memory in a process referred toherein as the “restore” process, after which, upon resetting the memorydevice at event 110, the memory device may be reset to the initial state(event 102), where the nonvolatile memory is placed in a predeterminedstate, and again operates in a volatile mode, like an SRAM or DRAMmemory device, event 104.

FIG. 2 shows an illustrative, non-exclusive example of an embodiment ofmemory cell 50. Cell 50 is formed in and/or on a substrate 12 of a firstconductivity type, such as a p-type conductivity type, for example.Substrate 12 may include any suitable substrate, illustrative,non-exclusive examples of which include silicon, germanium, silicongermanium, gallium arsenide, carbon nanotubes, and/or othersemiconductor materials.

Substrate 12 has a surface 14 and includes a buried layer 22 of a secondconductivity type, such as n-type conductivity type. Buried layer region22 may be formed using any suitable process and/or method performed onthe material of substrate 12, illustrative, non-exclusive examples ofwhich include ion implantation process and/or epitaxial growth.

Memory cell 50 includes a first region 16 having a second conductivitytype, such as n-type conductivity type, that is formed in substrate 12,and a second region 18 having a second conductivity type, that is formedin substrate 12 and spaced apart from the first region 16. First andsecond regions 16 and 18, respectively, are exposed at surface 14 andmay be formed using any suitable method and/or process, illustrative,non-exclusive examples of which include ion implantation, solid statediffusion, and/or epitaxial growth.

A floating body region 24 of the substrate 12 having a firstconductivity type, such as p-type conductivity type, is bounded bysurface 14, first and second regions 16 and 18, buried layer 22, andinsulating layer 26. The floating body region 24 may be formed using anysuitable method and/or process such as ion implantation, solid statediffusion, and/or epitaxial growth. Insulating layer 26 may be formedfrom any suitable insulating and/or dielectric materials, illustrative,one non-exclusive example of which includes silicon dioxide. Insulatinglayers 26 may insulate cell 50 from neighboring cells 50 when multiplecells 50 are joined in an array 80 to form a memory device 90, anexample of which is illustrated in FIGS. 5A-5C.

A gate 60 may be positioned in between regions 16 and 18, and above thesurface 14. Gate 60 is insulated from surface 14 by an insulating layer62. Insulating layer 62 may be formed from any suitable dielectricmaterial, illustrative, non-exclusive examples of which include siliconoxide, high-K dielectric materials, tantalum peroxide, titanium oxide,zirconium oxide, hafnium oxide, and/or aluminum oxide. Gate 60 may bemade from any suitable conductive material, illustrative, non-exclusiveexamples of which include a polysilicon material, a metal gateelectrode, tungsten, tantalum, titanium and/or their nitrides.

A resistive change memory element 40 is positioned above one of theregions having second conductivity type. The resistive change memoryelement is shown as a variable resistor in FIG. 2, and may be formed bybipolar resistive memory element, such as transition metal oxides,ferroelectric, and/or ferromagnetic materials. The resistivity state ofa bipolar resistive memory element depends on the polarity of thepotential difference or current flow across the bipolar resistive memoryelement. The resistive change memory element 40 is shown to beelectrically connected to the source line region 16 in FIG. 2.Alternatively, resistive change memory element 40 may be connected tothe bit line region 18. The resistive change memory element 40 iselectrically connected to the floating body transistor 20—whichcomprises of the first region 16, the floating body region 24, thesecond region 18, and the gate electrode 60—(see also the schematic viewof the memory cell 50 in FIG. 4A), and the separation distance betweenthe volatile memory (i.e. the floating body transistor 20) and thenon-volatile memory (i.e. the resistive change memory element 40) can besmall, for example from about 90 nm to about 1 μm, preferably from about90 nm to about 500 nm, more preferably from about 90 nm to about 100 nmif the resistive change element 40 is located between the surface 14 andthe bottom-most (or first) metal layer for a 28-nm technology, or lessthan 1 um if the resistive change element 40 is located below the fourthmetal layer for a 28-nm technology process, or less than 10 um,depending on for example which metal layer the addressable line (e.g.source line 72) is implemented at as well as the process technologynode. Cell 50 further includes a word line (WL) terminal 70 electricallyconnected to gate 60, a source line (SL) terminal 72 electricallyconnected to region 16, a bit line (BL) terminal 74 electricallyconnected to region 18, a buried well (BW) terminal 76 electricallyconnected to buried layer region 22, and a substrate terminal 78electrically connected to substrate 12. Alternatively, the SL terminal72 may be electrically connected to region 18 and BL terminal 74 may beelectrically connected to region 16.

As discussed in more detail herein, the conductivity types describedabove are exemplary conductivity types and other conductivity typesand/or relative conductivity types are also within the scope of thepresent disclosure. As an illustrative, non-exclusive example, memorycell 50 may have and/or include a p-type conductivity type as the firstconductivity type and n-type conductivity type as the secondconductivity type.

Substrate 12 is present at all locations under array 80 (see FIG. 5A).Persons of ordinary skill in the art will appreciate that one or moresubstrate terminals 78 will be present in one or more locations as amatter of design choice. Such skilled persons will also appreciate thatwhile exemplary array 80 is shown as a single continuous array in FIGS.5A-5C, that many other organizations and layouts are possible like, forexample, word lines may be segmented or buffered, bit lines may besegmented or buffered, source lines may be segmented or buffered, thearray 80 may be broken into two or more sub-arrays, control circuitssuch as word decoders, column decoders, segmentation devices, senseamplifiers, write amplifiers may be arrayed around exemplary array 80 orinserted between sub-arrays of array 80. Thus the exemplary embodiments,features, design options, etc., described are not limiting in any way.

A non-limiting embodiment of a memory cell is shown in FIG. 3A. Theresistive change memory element 40 may comprise of an electrode 44 and abipolar resistive change material 46, which is connected to the secondconductivity region 16 through a conductive element 42, for example inthe form of a conductive plug. The resistive change memory element maybe connected to an addressable line through a conductive material 48.The conductive element 42 may be composed of conductive materials,illustrative, non-exclusive examples of which include tungsten,silicided silicon materials, aluminum or copper. Electrode 44 may beformed of conductive materials, illustrative, non-exclusive examples ofwhich include titanium nitride, titanium aluminum nitride, titaniumsilicon nitride, and/or platinum. Bipolar resistive change material 46is a material that may exhibit multiple resistivity values, and mayswitch the resistivity state based on the polarity of the potential orcurrent flow across the bipolar resistive element 46, illustrative,non-exclusive examples of which include transition metal oxides such astitanium oxide, nickel oxide, zirconium oxide, hafnium oxide, aluminumoxide, copper oxide (Cu_(x)O), copper manganese oxide (CuMnO_(x)),copper molybdenum oxide (CuMoO_(x)), indium zinc oxide (InZnO), and/orperovskites materials such as strontium titanium oxide (SrTiO₃),chromium-strontium zirconium oxide (Cr—SrZrO₃), praseodymium calciummanganese oxide (PrCaMnO₃), strontium lanthanum titanium oxide(SrLaTiO₃), lanthanum strontium iron oxide (LaSrFeO₃), lanthanumstrontium cobalt oxide (LaSrCrO₃). Alternatively the resistive changememory element 40 may comprise of a ferroelectric and/or ferromagneticmaterials. Electrode 48 may be formed by conductive materials,illustrative, non-exclusive examples of which include titanium nitride,titanium aluminum nitride, titanium silicon nitride, platinum, aluminumor copper, or layers of thereof.

In FIG. 3B, an alternative embodiment of memory cell 50 is shown wheresubstrate 12 is replaced by region 12A of the first conductivity type(for example, p-type) which is a well inside substrate 29 of the secondconductivity type (for example, n-type). The well 29 in turn could beanother well inside substrate 12B of the first conductivity type (forexample, p-type) as shown in FIG. 3B. This arrangement allows forsegmentation of the substrate terminal, which is connected to the region12A. The alternative embodiment of memory cell 50 shown in FIG. 3B alsoshows insulating layers 26 insulating both floating body region 24 andthe buried layer 22.

FIG. 3C illustrates an exemplary top view of memory cell 50. From a topview perspective, the memory cell 50 looks similar to a singletransistor. This is because each memory cell 50 includes a respectivevolatile memory portion and a respective non-volatile memory portionwithin a “single transistor” memory cell 50.

FIG. 4A illustrates an equivalent circuit representation of memory cell50. Inherent in memory cell 50 are metal-oxide-semiconductor (MOS)transistor 20, formed by source line region 16, gate 60, bit line region18, and floating body region 24; and bipolar devices 30 a and 30 b,formed by buried well region 22, floating body region 24, and bit lineregion 18 or source line region 16, respectively.

Also inherent in memory device 50 is bipolar device 30 c, formed bysource line region 16, floating body 24, and bit line region 18. Fordrawings clarity, bipolar device 30 c is shown separately in FIG. 4B.

In memory cell 50, the current may flow in either direction, from thebit line region 18 (connected to the BL terminal 74) to the source lineregion 16 (connected to the SL terminal 72), or vice versa. The MOStransistor 20 may also be asymmetric, as described for example in U.S.application Ser. No. 13/244,899 “Asymmetric Semiconductor Memory DeviceHaving Electrically Floating Body Transistor” (“Widjaja-3”), which ishereby incorporated herein, in its entirety, by reference thereto. Anasymmetric cell may conduct different amounts of current, depending onthe direction of the current flow.

FIG. 5A illustrates an integrated circuit device 90, which may compriseof memory array 80 formed by plurality of memory cells 50 arranged inrows and columns, and periphery circuitry, illustrative, non-exclusiveexamples of which include counter 82, read circuitry 84, write circuitry86, and address decoder 88. The memory array 80 may include at least 16memory cells 50, or up to and including 1 terabit of memory cells 50.The integrated circuit device 90 may be a memory device or an integratedcircuit device comprising of embedded memory, illustrative,non-exclusive examples of which include microprocessors, networking,communication, and field-programmable logic devices. The integratedcircuit device 90 may also comprise of circuitry to determine if memoryarray 80 (or a segment of memory array 80, for example when the segmentincludes at least 0.1% of the memory cells) has been idle for a periodof time, which may trigger a shadowing operation to conserve powerconsumption of the memory array 80 and subsequently the integratedcircuit device 90. The integrated circuit device 90 may also comprise ofa timer circuitry to ascertain that the elapsed idle time is greaterthan an elapsed time threshold, for example thirty seconds.

FIGS. 5B and 5C illustrate examples of memory arrays 80 and 81 formed bya plurality of memory cells 50. The memory array 81 shown in FIG. 5Ccomprises of links of a plurality memory cells 50 connected in parallel,for example as described in U.S. application Ser. No. 12/897,528“Compact Semiconductor Memory Device Having Reduced Number of Contacts,Methods of Operating and Methods of Making” (“Widjaja-6”), which ishereby incorporated herein, in its entirety, by reference thereto. Forsimplicity, only memory array 80 will be shown from hereon.

When power is applied to memory cell 50, memory cell 50 stores itsstates in floating body region 24 and may operate like a capacitorlessDRAM cell, with only one stable floating body state in a memory cell(for example as described in “A Capacitor-less 1T-DRAM Cell”, S. Okhoninet al., pp. 85-87, IEEE Electron Device Letters, vol. 23, no. 2,February 2002 (“Okhonin-1”), “Memory Design Using One-Transistor GainCell on SOI”, T. Ohsawa et al., pp. 152-153, Tech. Digest, 2002 IEEEInternational Solid-State Circuits Conference, February 2002(“Ohsawa-1”), “Further Insight Into the Physics and Modeling ofFloating-Body Capacitorless DRAMs”, A. Villaret et al., pp. 2447-2454,IEEE Transactions on Electron Devices, vol. 52, no. 11, November 2005(“Villaret”), “Scaled 1T-Bulk Devices Built with CMOS 90 nm Technologyfor Low-cost eDRAM Applications”, R. Ranica, et al., pp. 38-41, Tech.Digest, Symposium on VLSI Technology, 2005 (“Ranica”), and “Simulationof Intrinsic Bipolar Transistor Mechanisms for future capacitor-lesseDRAM on bulk substrate”, R. Pulicani et al., pp. 966-969, 2010 17^(th)IEEE International Conference on Electronics, Circuits, and Systems,December 2010 (“Pulicani”), which are hereby incorporated herein, intheir entireties, by reference thereto), or a bi-stable SRAM cell, wheremore than one stable state exists for each memory cell (for example asdescribed in U.S. Patent Application Publication No. 2010/00246284 toWidjaja et al., titled “Semiconductor Memory Having Floating BodyTransistor and Method of Operating” (“Widjaja-1”) and U.S. PatentApplication Publication No. 2010/0034041, “Method of OperatingSemiconductor Memory Device with Floating Body Transistor Using SiliconControlled Rectifier Principle” (“Widjaja-2”), which are both herebyincorporated herein, in their entireties, by reference thereto). In atleast one embodiment, the non-volatile memory element is initialized tohave a low resistivity state.

Several operations may be performed on memory cell 50 during thevolatile operation, such as holding, read, write logic-1, and writelogic-0 operations.

FIG. 6 schematically illustrates performance of a holding operation onmemory array 80, while FIG. 7 shows the bias applied on the terminals ofa memory cell 50 during the holding operation, according to anexemplary, non-limiting embodiment. The holding operation is performedby applying a positive back bias to the BW terminal 76, zero or negativebias on the WL terminal 70, zero voltage to BL terminal 74, SL terminal72, and substrate terminal 78. The positive back bias applied to theburied layer region 22 connected to the BW terminal 76 will maintain thestate of the memory cell 50 that it is connected to. The positive biasapplied to the BW terminal 76 needs to generate an electric fieldsufficient to trigger an impact ionization mechanism when the floatingbody region 24 is positively charged, as will be described through theband diagram shown in FIGS. 8A and 8B. The impact ionization rate as afunction of the electric field is for example described in “Physics ofSemiconductor Devices”, Sze S. M. and Ng K. K., which is herebyincorporated herein, in its entirety, by reference thereto.

In one embodiment the bias conditions for the holding operation onmemory cell 50 are: 0 volts is applied to WL terminal 70, 0 volts isapplied to BL terminal 74, 0 volts is applied to SL terminal 72, apositive voltage, for example, +1.2 volts is applied to BW terminal 76,and 0 volts is applied to the substrate terminal 78. In otherembodiments, different voltages may be applied to the various terminalsof memory cell 50 and the exemplary voltages described are not limiting.

FIG. 8A shows an energy band diagram characterizing the intrinsic n-p-nbipolar device 30 b when the floating body region 24 is positivelycharged and a positive bias voltage is applied to the buried well region22. The energy band diagram of the intrinsic n-p-n bipolar device 30 acan be constructed in a similar manner, with the source line region 16(connected to the SL terminal 72) in place of the bit line region 18(connected to the BL terminal 74). The dashed lines indicate the Fermilevels in the various regions of the n-p-n transistor 30 b. The Fermilevel is located in the band gap between the solid line 27 indicatingthe top of the valence band (the bottom of the band gap) and the solidline 29 indicating the bottom of the conduction band (the top of theband gap) as is well known in the art. If floating body 24 is positivelycharged, a state corresponding to logic-1, the bipolar transistors 30 aand 30 b will be turned on as the positive charge in the floating bodyregion lowers the energy barrier of electron flow into the base region.Once injected into the floating body region 24, the electrons will beswept into the buried well region 22 (connected to BW terminal 76) dueto the positive bias applied to the buried well region 22. As a resultof the positive bias, the electrons are accelerated and createadditional hot carriers (hot hole and hot electron pairs) through animpact ionization mechanism. The resulting hot electrons flow into theBW terminal 76 while the resulting hot holes will subsequently flow intothe floating body region 24. This process restores the charge onfloating body 24 and will maintain the charge stored in the floatingbody region 24 which will keep the n-p-n bipolar transistors 30 a and 30b on for as long as a positive bias is applied to the buried well region22 through BW terminal 76.

If floating body 24 is neutrally charged (the voltage on floating body24 being equal to the voltage on grounded bit line region 18), a statecorresponding to logic-0, no (or low) current will flow through then-p-n bipolar devices 30 a and 30 b. The bipolar devices 30 a and 30 bwill remain off and no impact ionization occurs. Consequently memorycells in the logic-0 state will remain in the logic-0 state.

FIG. 8B shows an energy band diagram of the intrinsic bipolar device 30a when the floating body region 24 is neutrally charged and a biasvoltage is applied to the buried well region 22. In this state theenergy level of the band gap bounded by solid lines 27A and 29A isdifferent in the various regions of n-p-n bipolar device 30 a. Becausethe potential of the floating body region 24 and the bit line region 18is equal, the Fermi levels are constant, resulting in an energy barrierbetween the bit line region 18 and the floating body region 24. Solidline 23 indicates, for reference purposes, the energy barrier betweenthe bit line region 18 and the floating body region 24. The energybarrier prevents electron flow from the bit line region 18 (connected toBL terminal 74) to the floating body region 24. Thus the n-p-n bipolardevice 30 a and 30 b will remain off.

In the holding operation described with regard to FIG. 6, there is noindividually selected memory cell. Rather the holding operation will beperformed at all cells connected to the same buried well terminal 76.

An alternative holding operation employing the intrinsic siliconcontrolled rectifier (SCR) device of memory cell, as described forexample in Widjaja-2, may also be performed on memory array 80.

The amount of charge stored in the floating body 24 can be sensed bymonitoring the cell current of the memory cell 50. If the memory cell isin a logic-1 state having holes in the floating body region 24, then thememory cell will have a lower threshold voltage (gate voltage where thetransistor is turned on), and consequently a higher cell current,compared to when the floating body memory cell 50 is in a logic-0 statehaving no holes in the floating body region 24.

FIG. 9A is a schematic view of a memory array 80 showing exemplary biasconditions for performing a read operation on the memory array 80,according to an embodiment of the present invention. FIG. 9B showsexemplary bias conditions applied to a selected memory cell 50 a duringthe read operation noted with regard to array 80 in FIG. 9A. The readoperation is performed by applying the following bias conditions: apositive bias to the WL terminal 70 a, a positive bias to the BLterminal 74 a, zero bias to the SL terminal 72 a, zero or positive biasto the BW terminal 76 a, and zero bias to the substrate terminal 78. Allunselected WL terminals 70 b (not shown) to 70 n have zero voltsapplied, all unselected BL terminals 74 b through 74 p have zero voltsapplied, all unselected SL terminals 72 b (not shown) through 72 n havezero volts applied.

In one embodiment the bias conditions for the read operation for memorycell 50 are: +1.2 volts is applied to WL terminal 70, +0.4 volts isapplied to BL terminal 74, 0.0 volts is applied to SL terminal 72, +1.2volts is applied to BW terminal 76, and 0.0 volts is applied to thesubstrate terminal 78. In other embodiments, different voltages may beapplied to the various terminals of memory cell 50 and the exemplaryvoltages described are not limiting. The positive voltage applied to BLterminal 74 may be less than the positive voltage applied to WL terminal70, in which the difference in the threshold voltage of the memory cell50 is employed to represent the state of the memory cell 50. Thepositive voltage applied to BL terminal 74 may also be greater than orequal to the positive voltage applied to WL terminal 70 and may generatean electric field sufficiently high to trigger the bipolar readmechanism.

A sensing circuit typically connected to BL terminal 74 can be used todetermine the data state of the memory cell 50. Any sensing scheme knownin the art can be used in conjunction with memory cell 50. For example,the sensing schemes disclosed in Ohsawa-1, Ohsawa-2, and/or Widjaja-3are incorporated by reference herein in their entireties.

FIG. 10A is a schematic illustration of a memory cell array showingexemplary bias conditions for a write logic-1 operation on the memoryarray 80 through an impact ionization mechanism, according to anembodiment of the present invention. FIG. 10B illustrates the biasconditions on an exemplary selected memory cell 50 a, according to theembodiment of FIG. 10A, where the following bias conditions are applied:a positive voltage is applied to the selected WL terminal 70, a positivevoltage is applied to the selected BL terminal 74, zero voltage isapplied to the selected SL terminal 72, zero or positive voltage isapplied to the selected BW terminal 76, and zero voltage is applied tothe substrate terminal 78. This positive voltage applied to the selectedBL terminal 74 a is greater than or equal to the positive voltageapplied to the selected WL terminal 70 a and may generate sufficientlyhigh enough electric field to trigger impact ionization mechanism.

In one particular non-limiting embodiment, about +1.2 volts is appliedto the selected WL terminal 70, about +1.2 volts is applied to theselected BL terminal 74, about 0.0 volts is applied to SL terminal 72,about 0.0 volts or +1.2 volts is applied to BW terminal 76, and about0.0 volts is applied to substrate terminal 78; while about 0.0 volts isapplied to the unselected WL terminals 70, unselected BL terminals 74,unselected SL terminals, and substrate terminal 78, and 0.0 volts or+1.2 volts is applied to BW terminal 76. These voltage levels areexemplary only and may vary from embodiment to embodiment. Thus theexemplary embodiments, features, bias levels, etc., described are notlimiting.

The positive bias applied to the selected BL terminal 74 will result ina depletion region around the bit line region 18. This effect issometimes referred to as drain induced barrier lowering (DIBL). As aresult, carriers (e.g. electrons) will flow through the selected memorycell 50 a from the SL terminal 72 a to the BL terminal 74 a. Electronswill be accelerated in the pinch-off region (defined as the region nearthe surface 14 where the channel concentration is equal to the bulkdoping concentration) of the MOS device 20, creating hot carriers(electron and hole pairs) in the vicinity of the bit line region 18. Thegenerated holes will then flow into the floating body 24, putting thecell 50 a to the logic-1 state.

FIG. 11A is a schematic illustration showing bias conditions for a writelogic-1 operation using band-to-band tunneling mechanism performed onmemory array 80 according to an embodiment of the present invention.FIG. 11B is a schematic cross-sectional view showing the bias conditionon an exemplary selected memory cell 50 a in the embodiment of array 80shown in FIG. 11A. A write logic-1 operation using band-to-bandtunneling mechanism can be performed by applying the following biasconditions: a negative voltage is applied to the selected WL terminal 70a, a positive voltage is applied to the selected BL terminal 74 a, zerovoltage is applied to the selected SL terminal 72 a, zero or positivevoltage is applied to the selected BW terminal 76 a, and zero voltage isapplied to the substrate terminal 78.

In one particular non-limiting embodiment, about −1.2 volts is appliedto the selected WL terminal 70 a, about +1.2 volts is applied to theselected BL terminal 74 a, about 0.0 volts is applied to SL terminal 72a, about 0.0 volts or +1.2 volts is applied to BW terminal 76 a, andabout 0.0 volts is applied to substrate terminal 78; while about 0.0volts is applied to the unselected WL terminals 70, unselected BLterminals 74, unselected SL terminals, and substrate terminal 78, and0.0 volts or +1.2 volts is applied to BW terminal 76. These voltagelevels are exemplary only may vary from embodiment to embodiment. Thusthe exemplary embodiments, features, bias levels, etc., described arenot limiting.

The negative charge on the gate 60 (connected to WL terminal 70) and thepositive voltage on bit line region 18 (connected to BL terminal 74)create a strong electric field (for example, about 10⁶ V/cm in silicon,as described in “Physics of Semiconductor Devices”, Sze S. M. and Ng K.K. (“Sze”), p. 104, hereby incorporated herein, by reference thereto)between the bit line region 18 and the floating body region 24 in theproximity of gate 60. This bends the energy band sharply upward near thegate and bit line junction overlap region, causing electrons to tunnelfrom the valence band to the conduction band, leaving holes in thevalence band. The electrons which tunnel across the energy band becomethe drain leakage current, while the holes are injected into floatingbody region 24 and become the hole charge that creates the logic-1state.

FIG. 12A is a schematic illustration showing bias conditions for a writelogic-0 operation performed on memory array 80 according to anembodiment of the present invention. FIG. 12B is a schematiccross-sectional illustration of bias conditions applied to an exemplaryselected memory cell 50 a from the memory array 80 of FIG. 12A. A writelogic-0 operation can be performed by applying a negative voltage biasto the selected SL terminal 72 a, a zero voltage bias to the WL terminal70 a, zero voltage bias to the BL terminal 74 a, zero or positivevoltage bias to the BW terminal 76 a, and zero voltage bias to thesubstrate terminal 78 a; while zero voltage is applied to the unselectedSL terminals 72, zero voltage bias is applied to the unselected WLterminals 70, zero or positive bias is applied to the BW terminal 76,and zero voltage bias is applied to the substrate 78. Under theseconditions, the p-n junction between floating body 24 and source lineregion 16 of the selected cell 50 is forward-biased, evacuating holesfrom the floating body 24. All memory cells 50 sharing the same selectedSL terminal 72 a will be written to simultaneously. To write arbitrarybinary data to different memory cells 50, a write logic-0 operation isfirst performed on all the memory cells to be written, followed by oneor more write logic-1 operations on the memory cells that must bewritten to logic-1.

In one particular non-limiting embodiment, about −1.2 volts is appliedto selected SL terminal 72 a, about 0.0 volts is applied to WL terminal70 a, about 0.0 volts is applied to BL terminal 74 a, about 0.0 volts or+1.2 volts is applied to BW terminal 76 a, and about 0.0 volts isapplied to substrate terminal 78, while zero voltage is applied to theunselected SL terminals 72, zero voltage bias is applied to theunselected WL terminals 70, zero or positive bias is applied to the BWterminal 76, and zero voltage bias is applied to the substrate 78. Thesevoltage levels are exemplary only and may vary from embodiment toembodiment. Thus the exemplary embodiments, features, bias levels, etc.,described are not limiting.

FIG. 13A is a schematic illustration showing bias conditions applied fora bit-selective write logic-0 operation performed on memory array 80according to an embodiment of the present invention. FIG. 13Billustrates bias conditions applied to the terminals of an exemplaryselected memory cell 50 a from the array 80 of FIG. 13A, which can maybe performed by applying a positive voltage to the selected WL terminal70 a, a negative voltage to the selected BL terminal 74 a, zero voltagebias to the selected SL terminal 72 a, zero or positive voltage bias tothe BW terminal 76 a, and zero voltage to the substrate terminal 78;while zero voltage is applied to the unselected WL terminals 70, zerovoltage is applied to the unselected BL terminals 74, zero voltage biasis applied to the unselected SL terminals 72, zero or positive voltageis applied to the BW terminal 76, and zero voltage is applied to thesubstrate terminal 78. When the potential of gate 60 (connected to WLterminal 70) is increased from zero (or negative voltage) to a positivevoltage, the floating body 24 potential will increase due to capacitivecoupling. As a result of the floating body 24 potential increase and thenegative voltage applied to the BL terminal 74, the p-n junction betweenfloating body region 24 and bit line region 18 is forward-biased,evacuating holes from the floating body 24.

To reduce undesired write logic-0 disturb to other memory cells 50 in amemory array 80, the applied potential can be optimized as follows: ifthe floating body 24 potential of state logic-1 is referred to asV_(FB1), then the voltage applied to the WL terminal 70 a is configuredto increase the floating body 24 potential by V_(FB1)/2 while −V_(FB1)/2is applied to BL terminal 74 a. Additionally, either ground or aslightly positive voltage may also be applied to the BL terminals 74 ofunselected memory cells 50 that do not share the same BL terminal 74 aas the selected memory cell 50 a, while a negative voltage may also beapplied to the WL terminals 70 of unselected memory cells 50 that do notshare the same WL terminal 70 a as the selected memory cell 50 a.

As illustrated in FIGS. 13A and 13B, the following exemplary biasconditions may be applied to the selected memory cell 50 a to perform abit-selective write logic-0 operation: a potential of about −0.2 voltsis applied to the selected BL terminal 74 a, a potential of about +1.2volts is applied to the selected WL terminal 70 a, about 0.0 volts isapplied to the selected SL terminal 72 a, a potential of about +1.2volts is applied to the BW terminal 76 a, and about 0.0 volts is appliedto the substrate terminal 78.

When power down is detected, e.g., when a user turns off the power tocell 50, or the power is inadvertently interrupted, or for any otherreason, power is at least temporarily discontinued to cell 50, datastored in the floating body region 24 is transferred to the resistancechange memory 40. This operation is referred to as “shadowing” and isdescribed with reference to FIGS. 14 and 15.

To perform a shadowing operation, a positive voltage is applied to theSL terminal 72, a positive voltage is applied to the WL terminal 70,zero voltage is applied to the BL terminal 74, zero or positive voltageis applied to the BW terminal 76, and zero voltage is applied to thesubstrate terminal 78. The positive voltage applied to the WL terminal70 is between the threshold voltage of the memory cell 50 in a logic-1state and the threshold voltage of the memory cell in a logic-0 state.The positive voltage applied to the SL terminal 72 generates an electricfield sufficiently high enough to trigger an impact ionization mechanismto further increase the current flow through the memory cell 50.

When the memory cell 50 is in a logic-1 state, current will flow throughthe memory cell 50 from the SL terminal 72 to the BL terminal 74 andpass through resistance change memory element 46 from the top electrode48 to the bottom electrode 44. The current flow through the memoryelement 46 is sufficient to switch the state of the resistance changememory 40 from a low resistivity state to a high resistivity state.Accordingly, the non-volatile resistance change memory 40 will be in ahigh resistivity state when the volatile memory of cell 50 is in alogic-1 state (i.e. floating body 24 is positively charged).

When the memory cell 50 is in a logic-0 state, no (or low) current willflow through the memory cell 50 because of the higher threshold voltageof the memory cell 50. Consequently, no (or low) current will flowthrough the resistance change memory element 46, and the resistancechange memory 40 will remain in a low resistivity state. Accordingly,the non-volatile resistance change memory 40 will be in a lowresistivity state when the volatile memory of cell 50 is in a logic-0state (i.e. floating body region 24 is neutral).

In one particular non-limiting example of this embodiment, about +1.2volts is applied to SL terminal 72, about +0.6 volts is applied to WLterminal 70, about 0.0 volts is applied to BL terminal 74, about +1.2volts is applied to BW terminal 76, and about 0.0 volts is applied tosubstrate terminal 78.

Note that this process occurs non-algorithmically, as the state of thefloating body 24 does not have to be read, interpreted, or otherwisemeasured to determine what state to write the non-volatile resistancechange memory 40 to. Rather, the shadowing process occurs automatically,driven by electric potential differences. Accordingly, this process isorders of magnitude faster than one that requires algorithmicintervention. In addition, no control circuitry, such as a memorycontroller, is required between the volatile memory component and thenon-volatile memory component, allowing for a close proximity betweenthe floating body transistor 20 and the resistance change element 40, asshown in FIGS. 3A and 3B.

Alternatively, a shadowing operation using intrinsic bipolar transistor30 b as the selection device to govern the switching (or non-switching)of the resistance change element 40 by applying the following biasconditions: a positive voltage is applied to the SL terminal 72, zerovoltage is applied to the BW terminal 76, and zero voltage is applied tothe substrate terminal 78. Zero voltage can be applied to WL terminal 70and BL terminal 74, or these terminals may be left floating.

When the memory cell 50 is in a logic-1 state, current will flow throughthe memory cell 50 from the SL terminal 72 to the BW terminal 76 andpass through resistance change memory element 46 from the top electrode48 to the bottom electrode 44. The current flow through the memoryelement 46 is sufficient to switch the state of the resistance changememory 40 from a low resistivity state to a high resistivity state.Accordingly, the non-volatile resistance change memory 40 will be in ahigh resistivity state when the volatile memory of cell 50 is in alogic-1 state (i.e. floating body 24 is positively charged). When thememory cell 50 is in a logic-0 state, no (or low) current will flowthrough the memory cell 50 because the low potential of the floatingbody region 24 will turn off bipolar transistor 30 b. Consequently, no(or low) current will flow through the resistance change memory element46, and the resistance change memory 40 will remain in a low resistivitystate. Accordingly, the non-volatile resistance change memory 40 will bein a low resistivity state when the volatile memory of cell 50 is in alogic-0 state (i.e. floating body region 24 is neutral).

In one particular non-limiting example of this embodiment, about +1.2volts is applied to SL terminal 72, about 0.0 volts is applied to BWterminal 76, and about 0.0 volts is applied to substrate terminal 78,while WL terminal 70 and BL terminal 74 are left floating.

When power is restored to cell 50, the state of the cell 50 as stored onthe non-volatile resistance change memory 40 is restored into floatingbody region 24. The restore operation (data restoration fromnon-volatile memory to volatile memory) is described with reference toFIGS. 16 and 17. In one embodiment, to perform the restore operation, anegative voltage is applied to the WL terminal 70, a positive voltage isapplied to the BL terminal 74, a negative voltage is applied to the SLterminal 72, zero or a positive voltage is applied to the BW terminal76, and zero voltage is applied to the substrate terminal 78.

These conditions will result in band-to-band tunneling hole injectioninto the floating body 24. However, if the resistance change memory isin a low resistivity state, the negative voltage applied to the SLterminal 72 will evacuate holes in the floating body 24 because the p-njunction formed by the floating body 24 and the source line region 16 isforward-biased. Consequently, the volatile memory state of memory cell50 will be restored to a logic-0 state upon completion of the restoreoperation, restoring the state that the memory cell 50 held prior to theshadowing operation.

If the resistance change memory 40 is in a high resistivity state, alarger voltage drop will develop across the resistance change memory 40and no (or low) current flows through the resistance change memory 40,hence the holes accumulated in the floating body 24 will not beevacuated. As a result, the memory logic-1 state that the memory cell 50held prior to the shadowing operation will be restored.

In one particular non-limiting example of this embodiment, about −1.2volts is applied to the SL terminal 72, about +1.2 volts is applied toterminal 74, about −1.2 volts is applied to terminal 70, about +1.2volts is applied to terminal 76, and about 0.0 volts is applied to thesubstrate terminal 78. However, these voltage levels may vary, whilemaintaining the relative relationships between the charges applied, asdescribed above.

Note that this process occurs non-algorithmically, as the state of thenon-volatile resistance change memory 40 does not have to be read,interpreted, or otherwise measured to determine what state to restorethe floating body 24 to. Rather, the restoration process occursautomatically, driven by resistivity state differences. Accordingly,this process is orders of magnitude faster than one that requiresalgorithmic intervention. In addition, no control circuitry, such as amemory controller, is required between the volatile memory component andthe non-volatile memory component, allowing for a close proximitybetween the floating body transistor 20 and the resistance changeelement 40, as shown in FIGS. 3A and 3B.

After restoring the memory cell(s) 50, the resistance change memory(ies)40 is/are reset to a predetermined state, e.g., a low resistivity state,so that each resistance change memory 40 has a known state prior toperforming another shadowing operation.

FIGS. 18 and 19 illustrate a reset operation performed on a memory array80 and a memory cell 50, respectively. To perform a reset operation, apositive voltage is applied to the BL terminal 74, a positive voltage isapplied to the WL terminal 70, zero voltage is applied to the SLterminal 72, zero or positive voltage is applied to the BW terminal 76,and zero voltage is applied to the substrate terminal 78. The positivevoltage applied to the WL terminal 70 is between the threshold voltageof the memory cell 50 in a logic-1 state and the threshold voltage ofthe memory cell in a logic-0 state. The positive voltage applied to theBL terminal 74 generates an electric field sufficiently high enough totrigger an impact ionization mechanism to further increase the currentflow through the memory cell 50.

When the memory cell 50 is in a logic-1 state, current will flow throughthe memory cell 50 from the BL terminal 74 to the SL terminal 72 andpass through resistance change memory element 46 from the bottomelectrode 44 to the top electrode 48. The current flow through thememory element 46 is sufficient to switch the state of the resistancechange memory 40 from a high resistivity state to a low resistivitystate. Accordingly, the non-volatile resistance change memory 40 will bein a low resistivity state when the volatile memory of cell 50 is in alogic-1 state (i.e. floating body 24 is positively charged). Note thatthe current flow (or voltage difference between the top electrode andbottom electrode of the resistance change memory 40) direction duringthe reset operation is the opposite of that during the shadowingoperation. The floating body transistor 20 allows for current flow inboth directions, depending on the mode of operations of the memory cell50.

When the memory cell 50 is in a logic-0 state, no (or low) current willflow through the memory cell 50 because of the higher threshold voltageof the memory cell 50. Consequently, no (or low) current will flowthrough the resistance change memory element 46 and the resistancechange memory 40 will remain in a low resistivity state. Accordingly,the non-volatile resistance change memory 40 will be in a lowresistivity state when the volatile memory of cell 50 is in a logic-0state (i.e. floating body region 24 is neutral).

In one particular non-limiting example of this embodiment, about 0.0volts is applied to SL terminal 72, about +0.6 volts is applied to WLterminal 70, about +1.2 volts is applied to BL terminal 74, about +1.2volts is applied to BW terminal 76, and about 0.0 volts is applied tosubstrate terminal 78.

Alternatively, a reset operation using intrinsic bipolar transistor 30 bas the selection device to govern the switching (or non-switching) ofthe resistance change element 40 by applying the following biasconditions: a positive voltage is applied to the BW terminal 76, zerovoltage is applied to the SL terminal 72, and zero voltage is applied tothe substrate terminal 78. Zero voltage can be applied to WL terminal 70and BL terminal 74, or these terminals may be left floating.

When the memory cell 50 is in a logic-1 state, current will flow throughthe memory cell 50 from the BW terminal 76 to the SL terminal 72 andpass through resistance change memory element 46 from the bottomelectrode 44 to the top electrode 48. The current flow through thememory element 46 is sufficient to switch the state of the resistancechange memory 40 from a high resistivity state to a low resistivitystate. Accordingly, the non-volatile resistance change memory 40 will bein a low resistivity state when the volatile memory of cell 50 is in alogic-1 state (i.e. floating body 24 is positively charged). Note thatthe current flow (or voltage difference between the top electrode andbottom electrode of the resistance change memory 40) direction duringthe reset operation is the opposite of that during the shadowingoperation. The bipolar transistor 30 b allows for current flow in bothdirections, depending on the mode of operations of the memory cell 50.

When the memory cell 50 is in a logic-0 state, no (or low) current willflow from the BW terminal 76 to the SL terminal 72 because the lowpotential of the floating body region 24 will turn off bipolartransistor 30 b. Consequently, no (or low) current will flow through theresistance change memory element 46 and the resistance change memory 40will remain in a low resistivity state. Accordingly, the non-volatileresistance change memory 40 will be in a low resistivity state when thevolatile memory of cell 50 is in a logic-0 state (i.e. floating bodyregion 24 is neutral).

In one particular non-limiting example of this embodiment, about 0.0volts is applied to SL terminal 72, about +1.2 volts is applied to BWterminal 76, and about 0.0 volts is applied to substrate terminal 78,while WL terminal 70 and BL terminal 74 are left floating.

Memory cell 50 may alternatively be fabricated on a silicon-on-insulator(SOI) substrate as illustrated in FIG. 20, where a buried insulator 22,an illustrative, non-exclusive example of which includes a buried oxidelayer, bounds the floating body 24 at the bottom.

In addition, memory cell 50 may alternatively comprise athree-dimensional structure as shown in FIGS. 21A and 21B, where thememory cell 50 comprise a fin structure 52, extending substantiallyperpendicular to, and above the top surface of the substrate 12/buriedinsulator 22.

In another alternative embodiment, memory cell 50 may be insulated fromneighboring memory cells 50 by an insulating layer 26 and a shallowerinsulating layer 28, as shown in FIG. 22, where the shallower insulatinglayer 28 is shown in dashed lines. The shallower insulating layer 28insulates the floating body region 24, but allows the buried layer 22 tobe continuous in the perpendicular direction of the cross-sectional viewshown in FIG. 22. Since the buried layer 22 of memory cells 50 iscontinuous in one direction, but is insulated in the other perpendiculardirection (by the insulating layer 26), buried layer 22 may be used inmemory cell access selection and define a row (or column) direction.Memory cell 50 may then operate in volatile mode independent of theresistivity state of the resistance change memory 40. The volatile modeoperation of memory cell 50 will be similar to the half-transistorfloating body memory cell, defined by the gate 60, bit line region 18,buried well region 22, as described for example in U.S. application Ser.No. 12/897,538, “A Semiconductor Memory Device Having an ElectricallyFloating Body Transistor” (“Widjaja-4”), and in U.S. application Ser.No. 12/897,516, “A Semiconductor Memory Device Having an ElectricallyFloating Body Transistor” (“Widjaja-5), both which are herebyincorporated herein, in their entireties, by reference thereto.

In another alternative embodiment, the initial state of the resistancechange memory element 40 may be in a high resistivity state. In thisembodiment, due to the a high resistance memory element 40 electricallyconnected to the SL terminal 72, the volatile operation of memory cell50 may employ the silicon controlled rectifier (SCR) principle asdescribed, for example, in Widjaja-2, or the half-transistor floatingbody memory cell described, for example, in Widjaja-4 and Widjaja-5. Thevolatile operation of memory cell 50 will utilize WL terminal 70, BLterminal 74, BW terminal 76, and substrate terminal 78.

To perform a shadowing operation, a positive voltage is applied to theBL terminal 74, a positive voltage is applied to the WL terminal 70,zero voltage is applied to the SL terminal 72, zero or positive voltageis applied to the BW terminal 76, and zero voltage is applied to thesubstrate terminal 78. The positive voltage applied to the WL terminal70 is between the threshold voltage of the memory cell 50 in a logic-1state and the threshold voltage of the memory cell in a logic-0 state.The positive voltage applied to the BL terminal 74 generates an electricfield sufficiently high enough to trigger an impact ionization mechanismto further increase the current flow through the memory cell 50.

When the memory cell 50 is in a logic-1 state, current will flow throughthe memory cell 50 from the BL terminal 74 to the SL terminal 72 andpass through resistance change memory element 46 from the bottomelectrode 44 to the top electrode 48. The current flow through thememory element 46 is sufficient to switch the state of the resistancechange memory 40 from a high resistivity state to a low resistivitystate. Accordingly, the non-volatile resistance change memory 40 will bein a low resistivity state when the volatile memory of cell 50 is in alogic-1 state (i.e. floating body 24 is positively charged).

When the memory cell 50 is in a logic-0 state, no (or low) current willflow through the memory cell 50 because of the higher threshold voltageof the memory cell 50. Consequently, no (or low) current will flowthrough the resistance change memory element 46 and the resistancechange memory 40 will remain in a low resistivity state. Accordingly,the non-volatile resistance change memory 40 will remain in a highresistivity state when the volatile memory of cell 50 is in a logic-0state (i.e. floating body region 24 is neutral).

In one particular non-limiting example of this embodiment, about 0.0volts is applied to SL terminal 72, about +0.6 volts is applied to WLterminal 70, about +1.2 volts is applied to BL terminal 74, about +1.2volts is applied to BW terminal 76, and about 0.0 volts is applied tosubstrate terminal 78.

Note that this process occurs non-algorithmically, as the state of thefloating body 24 does not have to be read, interpreted, or otherwisemeasured to determine what state to write the non-volatile resistancechange memory 40 to. Rather, the shadowing process occurs automatically,driven by electric potential differences. Accordingly, this process isorders of magnitude faster than one that requires algorithmicintervention. In addition, no control circuitry, such as a memorycontroller, is required between the volatile memory component and thenon-volatile memory component, allowing for a close proximity betweenthe floating body transistor 20 and the resistance change element 40, asshown in FIGS. 3A and 3B. A restore operation may be performed using aband-to-band tunneling operation by applying the following biasconditions: a negative voltage is applied to the WL terminal 70, apositive voltage is applied to the SL terminal 72, zero voltage isapplied to the BL terminal 74, zero or positive voltage is applied tothe BW terminal 76, and zero voltage is applied to the substrateterminal 78.

If resistance change memory element 40 is in a low resistivity state,these conditions will result in result in band-to-band tunneling holeinjection into the floating body 24. However, if the resistance changememory is in a high resistivity state, the SL terminal 72 acts as anopen circuit, and as a result, the electric field in the source lineregion 16 near the gate 60 is not sufficient to generate holes throughband-to-band tunneling mechanism.

In one particular non-limiting example of this embodiment, about −1.2volts is applied to the WL terminal 70, about +1.2 volts is applied toSL terminal 72, about 0.0 volts is applied to BL terminal 74, about +1.2volts is applied to BW terminal 76, and about 0.0 volts is applied tosubstrate terminal 78.

Note that this process occurs non-algorithmically, as the state of thefloating body 24 does not have to be read, interpreted, or otherwisemeasured to determine what state to write the non-volatile resistancechange memory 40 to. Rather, the restore process occurs automatically,driven by electric potential differences. Accordingly, this process isorders of magnitude faster than one that requires algorithmicintervention. In addition, no control circuitry, such as a memorycontroller, is required between the volatile memory component and thenon-volatile memory component, allowing for a close proximity betweenthe floating body transistor 20 and the resistance change element 40, asshown in FIGS. 3A and 3B.

To perform a reset operation, a positive voltage is applied to the SLterminal 72, a positive voltage is applied to the WL terminal 70, zerovoltage is applied to the BL terminal 74, zero or positive voltage isapplied to the BW terminal 76, and zero voltage is applied to thesubstrate terminal 78. The positive voltage applied to the WL terminal70 is between the threshold voltage of the memory cell 50 in a logic-1state and the threshold voltage of the memory cell in a logic-0 state.The positive voltage applied to the SL terminal 72 generates an electricfield sufficiently high enough to trigger an impact ionization mechanismto further increase the current flow through the memory cell 50.

When the memory cell 50 is in a logic-1 state, current will flow throughthe memory cell 50 from the SL terminal 72 to the BL terminal 74 andpass through resistance change memory element 46 from the top electrode48 to the bottom electrode 44. The current flow through the memoryelement 46 is sufficient to switch the state of the resistance changememory 40 from a low resistivity state to a high resistivity state.

When the memory cell 50 is in a logic-0 state, no (or low) current willflow through the memory cell 50 because of the higher threshold voltageof the memory cell 50. Consequently, no (or low) current will flowthrough the resistance change memory element 46 and the resistancechange memory 40 will remain in a high resistivity state. Accordingly,all the non-volatile resistance change memory 40 will be initialized toa high resistivity state.

In one particular non-limiting example of this embodiment, about +1.2volts is applied to SL terminal 72, about +0.6 volts is applied to WLterminal 70, about 0.0 volts is applied to BL terminal 74, about +1.2volts is applied to BW terminal 76, and about 0.0 volts is applied tosubstrate terminal 78.

Note that this process occurs non-algorithmically, as the state of thefloating body 24 does not have to be read, interpreted, or otherwisemeasured to determine what state to write the non-volatile resistancechange memory 40 to. Rather, the reset process occurs automatically,driven by electric potential differences. Accordingly, this process isorders of magnitude faster than one that requires algorithmicintervention. In addition, no control circuitry, such as a memorycontroller, is required between the volatile memory component and thenon-volatile memory component, allowing for a close proximity betweenthe floating body transistor 20 and the resistance change element 40, asshown in FIGS. 3A and 3B.

The integrated circuit device 90 may also comprise of a counter circuit82, which may determine if a memory cell 50 (or a group of memory cells50, the group may comprise of for example a row of memory cells 50 or afew rows of memory cells 50) is in volatile mode operation and has notbeen accessed for a certain period of time, for example, one second,although this predetermined time period may vary as a matter of designchoice. Once the memory cell 50 is idle for greater than an elapsed timethreshold (i.e., the predetermined time period), the memory cell 50 (ora group of memory cells 50) may be put into the non-volatile statethrough the shadowing operation. Since memory cell 50 does not requirepower to maintain its states, this operation thus results in a loweroperating power of the integrated circuit device 90.

FIG. 23 shows an illustrative, non-exclusive example of an embodiment ofmemory cell 35. Cell 35 is formed in and/or on a substrate 12 of a firstconductivity type, such as a p-type conductivity type, for example.Substrate 12 may include any suitable substrate, illustrative,non-exclusive examples of which include silicon, germanium, silicongermanium, gallium arsenide, carbon nanotubes, and/or othersemiconductor materials. In some embodiments of the invention, substrate12 may be the bulk material of the semiconductor wafer. In otherembodiments, substrate 12 can may be a well of the first conductivitytype embedded in either a well of the second conductivity type or,alternatively, in the bulk of the semiconductor wafer of the secondconductivity type, such as n-type, for example, (not shown in thefigures). To simplify the description, the substrate 12 will usually bedrawn as the semiconductor bulk material as it is in FIG. 23.

Substrate 12 has a surface 14 and includes a buried layer 22 of a secondconductivity type, such as n-type conductivity type. Buried layer region22 may be formed using any suitable process and/or method performed onthe material of substrate 12, illustrative, non-exclusive examples ofwhich include ion implantation process and/or epitaxial growth. Buriedlayer region 22 is bounded on the side by insulating layer 26.Insulating layer 26 may be formed from any suitable insulating and/ordielectric materials, one illustrative, non-exclusive example of whichincludes silicon dioxide.

Memory cell 35 includes a first region 16 having a second conductivitytype, such as n-type conductivity type, that is formed in substrate 12,and a second region 18 having a second conductivity type, that is formedin substrate 12 and spaced apart from the first region 16. First andsecond regions 16 and 18, respectively, are exposed at surface 14 andmay be formed using any suitable method and/or process, illustrative,non-exclusive examples of which include ion implantation, solid statediffusion, and/or epitaxial growth.

A floating body region 24 of the substrate 12 having a firstconductivity type, such as p-type conductivity type, is bounded bysurface 14, first and second regions 16 and 18, buried layer 22, andinsulating layer 26. The floating body region 24 may be formed using anysuitable method and/or process such as ion implantation, solid statediffusion, and/or epitaxial growth. Insulating layers 26 may insulatecell 35 from neighboring cells 35 when multiple cells 35 are joined inan array 80 to form a memory device 90 as illustrated in FIG. 25.

A gate 60 may be positioned in between regions 16 and 18, and above thesurface 14. Gate 60 is insulated from surface 14 by an insulating layer62. Insulating layer 62 may be formed from any suitable dielectricmaterial, illustrative, non-exclusive examples of which include siliconoxide, high-K dielectric materials, tantalum peroxide, titanium oxide,zirconium oxide, hafnium oxide, and/or aluminum oxide. Gate 60 may bemade from any suitable conductive material, illustrative, non-exclusiveexamples of which include a polysilicon material, a metal gateelectrode, tungsten, tantalum, titanium and/or their nitrides.

Cell 35 further includes a word line (WL) terminal 70 electricallyconnected to gate 60, a source line (SL) terminal 72 electricallyconnected to region 16, a bit line (BL) terminal 74 electricallyconnected to region 18, and a substrate terminal 78 electricallyconnected to substrate 12. The floating body region 24 and buried layerregion 22 are not connected to any terminals and may be consideredfloating.

As discussed in more detail herein, the conductivity types describedabove are exemplary conductivity types and other conductivity typesand/or relative conductivity types are also within the scope of thepresent disclosure. As an illustrative, non-exclusive example, memorycell 35 may have and/or include a p-type conductivity type as the firstconductivity type and n-type conductivity type as the secondconductivity type.

FIG. 24A illustrates an equivalent circuit representation of memory cell35. Inherent in memory cell 35 are metal-oxide-semiconductor (MOS)transistor 20, formed by source line region 16, gate 60, bit line region18, and floating body region 24, and silicon controlled rectifier (SCR)p-n-p-n devices 30 a and 30 b formed by substrate 12, buried well layer22, floating body 24, and source line region 16 and bit line region 18,respectively. The SCR device 30 a is formed by the interacting n-p-nbipolar device 31 a (formed by source line region 16, floating body 24,and buried layer 22) and p-n-p bipolar device 31 c (formed by floatingbody 24, buried layer 22, and substrate 12), while the SCR device 30 bis formed by the interacting n-p-n bipolar device 31 b (formed by bitline region 18, floating body 24, and buried layer 22) and p-n-p bipolardevice 31 c.

FIG. 24B also illustrates another equivalent circuit representation ofmemory cell 35, where the SCR device 30 a and 30 b are illustrated asback-to-back p-n diodes. The SCR device 30 a is formed by the p-n diodes31 d (formed by floating body 24 and source line region 16) and 31 f(formed by substrate 12 and buried well 22), while the SCR device 30 ais formed by the p-n diodes 31 e (formed by floating body 24 and bitline region 18) and 31 f.

Also inherent in memory device 35 is bipolar device 30 c, formed bysource line region 16, floating body 24, and bit line region 18. Fordrawings clarity, bipolar device 30 c is shown separately in FIG. 24C.

In memory cell 35, the current may flow in either direction, from thebit line region 18 (connected to the BL terminal 74) to the source lineregion 16 (connected to the SL terminal 72), or vice versa. The MOStransistor 20 may also be asymmetric, as described for example in U.S.application Ser. No. 13/244,899 “Asymmetric Semiconductor Memory DeviceHaving Electrically Floating Body Transistor” (“Widjaja-3”), which ishereby incorporated herein, in its entirety, by reference thereto. Anasymmetric cell may conduct different amounts of current, depending onthe direction of the current flow.

FIG. 25 illustrates an integrated circuit device 90, which may compriseof memory array 80 formed by plurality of memory cells 35 arranged inrows and columns, and periphery circuitry, illustrative, non-exclusiveexamples of which include reference cell 82, read circuitry 84, writecircuitry 86, and address decoder 88. The memory array 80 may include atleast 16 memory cells 35, or up to and including 1 terabit of memorycells 35. The integrated circuit device 90 may be a memory device or anintegrated circuit device comprising of embedded memory, illustrative,non-exclusive examples of which include microprocessors, networking,communication, and field-programmable logic devices. FIGS. 26A and 26Billustrate examples of memory arrays 80 and 81 formed by a plurality ofmemory cells 35. The memory array 81 shown in FIG. 26B comprises oflinks of a plurality of memory cells 35 connected in parallel, forexample as described in U.S. application Ser. No. 12/897,528 “CompactSemiconductor Memory Device Having Reduced Number of Contacts, Methodsof Operating and Methods of Making” (“Widjaja-6”), which is herebyincorporated herein, in its entirety, by reference thereto. Forsimplicity, only memory array 80 will be shown from hereon.

Several operations may be performed on memory cell 35 during, such asholding, read, write logic-1, and write logic-0 operations. FIG. 27schematically illustrates performance of a holding operation on memoryarray 80, while FIG. 28 shows the bias applied on the terminals of amemory cell 35 during the holding operation, according to an exemplary,non-limiting embodiment. The holding operation is performed by applyinga positive back bias to the substrate terminal 78, and zero or negativebias on the WL terminal 70, zero voltage to BL terminal 74 and SLterminal 72. The positive back bias applied to the substrate region 12connected to the substrate terminal 78 will maintain the state of thememory cell 35 that it is connected to.

If cell 35 is in logic-1 having holes in the floating body region 24,the SCR devices 30 a or 30 b formed by substrate 12, buried layer 22,floating body region 24, and source line region 16 or bit line region 18will be turned on, thereby maintaining logic-1 state. Memory cells inlogic-0 state will remain turned off since the potential of the floatingbody region 24 is not high enough for the SCR device 30 a or 30 b toconduct. Accordingly these cells maintain the logic-0 data. In thismanner, a memory array 80 comprising of a plurality of memory cells 35may be maintained by applying a positive bias to the substrate terminal78.

In one embodiment the bias conditions for the holding operation onmemory cell 35 are: 0 volts is applied to WL terminal 70, 0 volts isapplied to BL terminal 74, 0 volts is applied to SL terminal 72, apositive voltage, for example, +1.2 volts is applied to the substrateterminal 78. In other embodiments, different voltages may be applied tothe various terminals of memory cell 35 and the exemplary voltagesdescribed are not limiting.

In another embodiment, a memory array 80 comprising of a plurality ofmemory cells 35 may be refreshed by periodically applying a positivevoltage pulse through the substrate terminal 78. An example of a refreshscheme is shown in FIG. 29. A reference cell 35R1 or 35R2, shown inFIGS. 30 and 31, respectively, provides an electrical contact to thefloating body region 24, for example through the sense line terminal 73.As a result, the floating body 24 potential of a reference cell 35R1 or35R2 may be compared with a reference value V_(REF). If the potential ofthe reference cell 35R1 or 35R2 is less than the reference valueV_(REF), a positive pulse is applied to the substrate terminal 78 torefresh the state of the memory cells 35. If the state of the referencecell 35R1 or 35R2 is greater than the reference value V_(REF), zerovoltage is applied to the substrate terminal 78.

FIG. 30 schematically illustrates a reference cell 35R1. A sense lineregion 20 of a first conductivity type, such as p-type, for example isalso provided in floating body region 24 and is exposed at surface 14.Sense line region 20 may be formed using any suitable method and/orprocess, illustrative, non-exclusive examples of which include ionimplantation, solid state diffusion, and/or epitaxial growth. The senseline region 20 has the same conductivity type as the floating bodyregion 24, and the sense line region 20 may be more heavily doped thanthe floating body region 24. The sense line region 20 allows for anelectrical connection to the floating body region 24. The sense lineregion 20 is shown connected to a sense line terminal 73.

FIG. 31 schematically illustrates a schematic top view reference cell35R2 according to another embodiment of the present invention. Referencecell 35R2 may be subdivided to include a region comprising of memorycell 35, as indicated by the region enclosed by dashed lines in FIG. 31.The reference cell 35R2 also comprise of a sense region 20, which islocated adjacent to the memory cell 35. FIGS. 32A and 32B are schematic,cross-section illustrations of reference cell 35R2 along the I-I′ andII-II′ cut lines of FIG. 31, respectively.

The amount of charge stored in the floating body 24 can be sensed bymonitoring the cell current of the memory cell 35. If the memory cell isin a logic-1 state having holes in the floating body region 24, then thememory cell 35 will have a lower threshold voltage (gate voltage wherethe transistor is turned on), and consequently a higher cell current,compared to when the floating body memory cell 35 is in logic-0 statehaving no holes in the floating body region 24.

FIG. 33 is a schematic view of a memory array 80 showing exemplary biasconditions for performing a read operation on the memory array 80,according to an embodiment of the present invention. FIG. 34 showsexemplary bias conditions applied to a selected memory cell 35 a duringthe read operation noted with regard to array 80 in FIG. 33. The readoperation is performed by applying the following bias conditions: apositive bias to the WL terminal 70 a, a positive bias to the BLterminal 74 a, zero bias to the SL terminal 72 a, and zero or positivebias to the substrate terminal 78 a. All unselected WL terminals 70 b(not shown) to 70 n have zero volts applied, all unselected BL terminals74 b through 74 p have zero volts applied, all unselected SL terminals72 b (not shown) through 72 n have zero volts applied, while zero or apositive bias is applied to the unselected substrate terminals 78 b (notshown) through 78 n.

In one embodiment the bias conditions for the read operation for memorycell 35 are: +1.2 volts is applied to WL terminal 70, +0.4 volts isapplied to BL terminal 74, 0.0 volts is applied to SL terminal 72, and0.0 volts or +1.2 volts is applied to the substrate terminal 78. Inother embodiments, different voltages may be applied to the variousterminals of memory cell 35 and the exemplary voltages described are notlimiting. The positive voltage applied to BL terminal 74 may be lessthan the positive voltage applied to WL terminal 70, in which thedifference in the threshold voltage of the memory cell 35 is employed torepresent the state of the memory cell 35. The positive voltage appliedto BL terminal 74 may also be greater than or equal to the positivevoltage applied to WL terminal 70 and generates an electric fieldsufficiently high enough to trigger the bipolar read mechanism.

A sensing circuit typically connected to BL terminal 74 can be used todetermine the data state of the memory cell 35. Any sensing scheme knownin the art can be used in conjunction with memory cell 35. For example,the sensing schemes disclosed in Ohsawa-1, Ohsawa-2, and/or Widjaja-3are incorporated by reference herein in their entireties.

FIG. 35 is a schematic illustration of a memory cell array showingexemplary bias conditions for a write logic-1 operation on the memoryarray 80 through an impact ionization mechanism, according to anembodiment of the present invention. FIG. 36 illustrates the biasconditions on an exemplary selected memory cell 35 a, according to theembodiment of FIG. 35, where the following bias conditions are applied:a positive voltage is applied to the selected WL terminal 70, a positivevoltage is applied to the selected BL terminal 74, zero voltage isapplied to the selected SL terminal 72, and zero or positive voltage isapplied to the substrate terminal 78. This positive voltage applied tothe selected BL terminal 74 a is greater than or equal to the positivevoltage applied to the selected WL terminal 70 a and generates anelectric field sufficiently high enough to trigger an impact ionizationmechanism.

In one particular non-limiting embodiment, about +1.2 volts is appliedto the selected WL terminal 70, about +1.2 volts is applied to theselected BL terminal 74, about 0.0 volts is applied to SL terminal 72,and about 0.0 volts or +1.2 volts is applied to substrate terminal 78;while about 0.0 volts is applied to the unselected WL terminals 70,unselected BL terminals 74, unselected SL terminals, and 0.0 volts or+1.2 volts is applied to the unselected substrate terminal 78. Thesevoltage levels are exemplary only and may vary from embodiment toembodiment. Thus the exemplary embodiments, features, bias levels, etc.,described are not limiting.

The positive bias applied to the selected BL terminal 74 a will resultin a depletion region around the bit line region 18. This effect issometimes referred to as drain induced barrier lowering (DIBL). As aresult, carriers (e.g. electrons) will flow through the selected memorycell 35 a from the SL terminal 72 a to the BL terminal 74 a. Electronswill be accelerated in the pinch-off region (defined as the region nearthe surface 14 where the channel concentration is equal to the bulkdoping concentration) of the MOS device 20, creating hot carriers(electron and hole pairs) in the vicinity of the bit line region 18. Thegenerated holes will then flow into the floating body 24, putting thecell 35 a to the logic-1 state.

FIG. 37 is a schematic illustration showing bias conditions for a writelogic-1 operation using a band-to-band tunneling mechanism performed onmemory array 80 according to an embodiment of the present invention.FIG. 38 is a schematic view showing the bias conditions on an exemplaryselected memory cell 35 a in the embodiment of array 80 shown in FIG.37. A write logic-1 operation using a band-to-band tunneling mechanismcan be performed by applying the following bias conditions: a negativevoltage is applied to the selected WL terminal 70 a, a positive voltageis applied to the selected BL terminal 74 a, zero voltage is applied tothe selected SL terminal 72 a, and zero or positive voltage is appliedto the substrate terminal 78 a.

In one particular non-limiting embodiment, about −1.2 volts is appliedto the selected WL terminal 70 a, about +1.2 volts is applied to theselected BL terminal 74 a, about 0.0 volts is applied to SL terminal 72a, about 0.0 volts or +1.2 volts is applied to substrate terminal 78 a;while about 0.0 volts is applied to the unselected WL terminals 70,unselected BL terminals 74, unselected SL terminals, and 0.0 volts or+1.2 volts is applied to substrate terminal 78. These voltage levels areexemplary only may vary from embodiment to embodiment. Thus theexemplary embodiments, features, bias levels, etc., described are notlimiting.

The negative charge on the gate 60 (connected to WL terminal 70) and thepositive voltage on bit line region 18 (connected to BL terminal 74)create a strong electric field (for example, about 10⁶ V/cm in silicon,as described in “Physics of Semiconductor Devices”, Sze S. M. and Ng K.K. (“Sze”), p. 104, hereby incorporated herein, by reference thereto)between the bit line region 18 and the floating body region 24 in theproximity of gate 60. This bends the energy band sharply upward near thegate and bit line junction overlap region, causing electrons to tunnelfrom the valence band to the conduction band, leaving holes in thevalence band. The electrons which tunnel across the energy band becomethe drain leakage current, while the holes are injected into floatingbody region 24 and become the hole charge that creates the logic-1state.

FIG. 39 is a schematic illustration showing bias conditions for a writelogic-0 operation performed on memory array 80 according to anembodiment of the present invention. FIG. 40 is a schematic illustrationof bias conditions applied to an exemplary selected memory cell 35 afrom the memory array 80 of FIG. 39. A write logic-0 operation can beperformed by applying a negative voltage bias to the selected SLterminal 72 a, a zero voltage bias to the WL terminal 70 a, zero voltagebias to the BL terminal 74 a, zero or positive voltage bias to thesubstrate terminal 78 a; while zero voltage is applied to the unselectedSL terminals 72, zero voltage bias is applied to the unselected WLterminals 70, zero or positive bias is applied to the substrate 78.Under these conditions, the p-n junction between floating body 24 andsource line region 16 of the selected cell 35 is forward-biased,evacuating holes from the floating body 24. All memory cells 35 sharingthe same selected SL terminal 72 a will be written to simultaneously. Towrite arbitrary binary data to different memory cells 35, a writelogic-0 operation is first performed on all the memory cells to bewritten, followed by one or more write logic-1 operations on the memorycells that must be written to logic-1.

In one particular non-limiting embodiment, about −1.2 volts is appliedto selected SL terminal 72 a, about 0.0 volts is applied to WL terminal70 a, about 0.0 volts is applied to BL terminal 74 a, about 0.0 volts or+1.2 volts is applied to substrate terminal 78 a, while zero voltage isapplied to the unselected SL terminals 72, zero voltage bias is appliedto the unselected WL terminals 70, zero or positive bias is applied tothe substrate 78. These voltage levels are exemplary only and may varyfrom embodiment to embodiment. Thus the exemplary embodiments, features,bias levels, etc., described are not limiting.

FIG. 41 is a schematic illustration showing bias conditions applied fora bit-selective write logic-0 operation performed on memory array 80according to an embodiment of the present invention. FIG. 42 illustratesbias conditions applied to the terminals of an exemplary selected memorycell 35 a from the array 80 of FIG. 41, which can may be performed byapplying a positive voltage to the selected WL terminal 70 a, a negativevoltage to the selected BL terminal 74 a, zero voltage bias to theselected SL terminal 72 a, zero or positive voltage bias to thesubstrate terminal 78 a; while zero voltage is applied to the unselectedWL terminals 70, zero voltage is applied to the unselected BL terminals74, zero voltage bias is applied to the unselected SL terminals 72, zeroor positive voltage is applied to the substrate terminal 78. When thepotential of gate 60 (connected to WL terminal 70) is increased fromzero (or negative voltage) to a positive voltage, the floating body 24potential will increase due to capacitive coupling. As a result of thefloating body 24 potential increase and the negative voltage applied tothe BL terminal 74 a, the p-n junction between floating body region 24and bit line region 18 is forward-biased, evacuating holes from thefloating body 24.

To reduce undesired write logic-0 disturb to other memory cells 35 in amemory array 80, the applied potential can be optimized as follows: ifthe floating body 24 potential of state logic-1 is referred to asV_(FB1), then the voltage applied to the WL terminal 70 a is configuredto increase the floating body 24 potential by V_(FB1)/2 while −V_(FB1)/2is applied to BL terminal 74 a. Additionally, either ground or aslightly positive voltage may also be applied to the BL terminals 74 ofunselected memory cells 35 that do not share the same BL terminal 74 aas the selected memory cell 35 a, while a negative voltage may also beapplied to the WL terminals 70 of unselected memory cells 35 that do notshare the same WL terminal 70 a as the selected memory cell 35 a.

As illustrated in FIGS. 41 and 42, the following exemplary biasconditions may be applied to the selected memory cell 35 a to perform abit-selective write logic-0 operation: a potential of about −0.2 voltsis applied to the selected BL terminal 74 a, a potential of about +1.2volts is applied to the selected WL terminal 70 a, about 0.0 volts isapplied to the selected SL terminal 72 a, and a potential of about 0.0volts or +1.2 volts is applied to the substrate terminal 78 a.

FIG. 43 shows an illustrative, non-exclusive example of an embodiment ofmemory cell 150. Cell 150 is formed in and/or on a substrate 12 of afirst conductivity type, such as a p-type conductivity type, forexample. Substrate 12 may include any suitable substrate, illustrative,non-exclusive examples of which include silicon, germanium, silicongermanium, gallium arsenide, carbon nanotubes, and/or othersemiconductor materials.

Substrate 12 has a surface 14 and includes a buried layer 22 of a secondconductivity type, such as n-type conductivity type. Buried layer region22 may be formed using any suitable process and/or method performed onthe material of substrate 12, illustrative, non-exclusive examples ofwhich include ion implantation processing and/or epitaxial growthprocessing. Buried layer region 22 is bounded on the side by insulatinglayer 26. Insulating layer 26 may be formed from any suitable insulatingand/or dielectric materials, one illustrative, non-exclusive example ofwhich includes silicon dioxide.

Memory cell 150 includes a first region 16 having a second conductivitytype, such as n-type conductivity type, that is formed in substrate 12,and a second region 18 having a second conductivity type, that is formedin substrate 12 and spaced apart from the first region 16. First andsecond regions 16 and 18, respectively, are exposed at surface 14 andmay be formed using any suitable method and/or process, illustrative,non-exclusive examples of which include ion implantation, solid statediffusion, and/or epitaxial growth processes.

A floating body region 24 of the substrate 12 having a firstconductivity type, such as p-type conductivity type, is bounded bysurface 14, first and second regions 16 and 18, buried layer 22, andinsulating layer 26. The floating body region 24 may be formed using anysuitable method and/or process such as ion implantation, solid statediffusion, and/or epitaxial growth. Insulating layer 26 may be formedfrom any suitable insulating and/or dielectric materials, oneillustrative, non-exclusive example of which includes silicon dioxide.Insulating layers 26 may insulate cell 150 from neighboring cells 150when multiple cells 150 are joined in an array 80 to form a memorydevice 90, an example of which is illustrated in FIG. 46A.

A gate 60 may be positioned in between regions 16 and 18, and above thesurface 14. Gate 60 is insulated from surface 14 by an insulating layer62. Insulating layer 62 may be formed from any suitable dielectricmaterial, illustrative, non-exclusive examples of which include siliconoxide, high-K dielectric materials, tantalum peroxide, titanium oxide,zirconium oxide, hafnium oxide, and/or aluminum oxide. Gate 60 may bemade from any suitable conductive material, illustrative, non-exclusiveexamples of which include a polysilicon material, a metal gateelectrode, tungsten, tantalum, titanium and/or their nitrides.

A resistive change memory element 40 is positioned above one of theregions having second conductivity type. The resistive change memoryelement is shown as a variable resistor in FIG. 43, and may be formed byphase change memory element or unipolar or bipolar resistive memoryelement, such as transition metal oxides materials. The switching of theresistivity state of a bipolar resistive memory element depends on thepolarity of the potential difference or current flow across the bipolarresistive memory element, while the switching of a unipolar resistivememory element does not, for example as described in “Resistivenon-volatile memory devices (Invited Paper)”, R. Waser, pp. 1925-1928,Microelectronic Engineering, vol. 86, 2009, which is hereby incorporatedherein, in its entirety, by reference thereto. The resistive changememory element 40 is shown to be electrically connected to the sourceline region 16 in FIG. 43. Alternatively, resistive change memoryelement 40 may be connected to the bit line region 18. The resistivechange memory element 40 is electrically connected to the floating bodytransistor 20—which comprises of the first region 16, the floating bodyregion 24, the second region 18, and the gate electrode 60—(see also theschematic view of the memory cell 150 in FIG. 45), and the separationdistance between the volatile memory (i.e. the floating body transistor20) and the non-volatile memory (i.e. the resistive change memoryelement 40) can be small, for example from about 90 nm to about 1 μm,more preferably from about 90 nm to about 500 nm, even more preferablyfrom about 90 nm to about 100 nm if the resistive change element 40 islocated between the surface 14 and the bottom-most (or first) metallayer for a 28-nm technology, or less than 1 um if the resistive changeelement 40 is located below the fourth metal layer for a 28-nmtechnology process, or less than 10 um, depending on for example whichmetal layer the addressable line (e.g. source line 72) is implemented atas well as the process technology node, depending on, for example, whichmetal layer the addressable line (e.g. source line 72) is implementedat.

Cell 150 further includes a word line (WL) terminal 70 electricallyconnected to gate 60, a source line (SL) terminal 72 electricallyconnected to region 16, a bit line (BL) terminal 74 electricallyconnected to region 18, and a substrate terminal 78 electricallyconnected to substrate 12. Alternatively, the SL terminal 72 may beelectrically connected to region 18 and BL terminal 74 may beelectrically connected to region 16. The floating body region 24 andburied layer region 22 are not connected to any terminals and may beconsidered floating.

As discussed in more detail herein, the conductivity types describedabove are exemplary conductivity types and other conductivity typesand/or relative conductivity types are also within the scope of thepresent disclosure. As an illustrative, non-exclusive example, memorycell 150 may have and/or include a p-type conductivity type as the firstconductivity type and n-type conductivity type as the secondconductivity type.

A non-limiting embodiment of the memory cell is shown in FIG. 44A. Theresistive change memory element 40 may comprise of an electrode 44 and aphase change memory material 46, which is connected to the secondconductivity region 16 through a conductive element 42, for example inthe form of a conductive plug. The resistive change memory element maybe connected to an addressable line through a conductive material 48.The conductive element 42 may be composed of conductive materials,illustrative, non-exclusive examples of which include tungsten orsilicided silicon materials. Electrode 44 may be formed of conductivematerials, illustrative, non-exclusive examples of which includetitanium nitride, titanium aluminum nitride, titanium silicon nitride,and/or platinum. Resistive change material 46 is a material that mayexhibit multiple resistivity values. For the case of phase change memoryelements, the resistivity depends on the crystalline phase of thematerial, while for the metal oxide materials, the resistivity typicallydepends on the presence or absence of conductive filaments. Acrystalline phase of a phase change type resistive change materialexhibits a low resistivity (e.g., ˜1 kΩ) state and an amorphous phase ofthat material exhibits a high resistivity state (e.g., >100 kΩ).Examples of phase change material include alloys containing elementsfrom Column VI of the periodic table, such as GeSbTe alloys. Examples ofmetal-insulator-metal resistance change materials include a variety ofoxides such as Nb2O5, Al2O3, Ta2O5, TiO2, and NiO and perovskite metaloxides, such as SrZrO3, (Pr, Ca)MnO3 and SrTiO3:Cr. Electrode 48 may beformed of conductive materials, illustrative, non-exclusive examples ofwhich include titanium nitride, titanium aluminum nitride, titaniumsilicon nitride, platinum, aluminum or copper, or layers of thereof.

FIG. 44B illustrates an exemplary top view of memory cell 150. From atop view perspective, the memory cell 150 looks similar to a singletransistor. This is because each memory cell 150 includes a respectivevolatile memory portion and a respective nonvolatile memory portionwithin a “single transistor” memory cell 150.

FIG. 45 illustrates an equivalent circuit representation of memory cell150. Memory cell 150 comprises of memory cell 35 along with theresistive change memory element 40.

FIG. 46A illustrates an integrated circuit device 90, which may compriseof memory array 80 formed by plurality of memory cells 150 arranged inrows and columns, and periphery circuitry, illustrative, non-exclusiveexamples of which include counter 82, read circuitry 84, write circuitry86, and address decoders 88. The memory array 80 may include at least 16memory cells 150, or up to and including 1 terabit of memory cells 150.The integrated circuit device 90 may be a memory device or an integratedcircuit device comprising of embedded memory, illustrative,non-exclusive examples of which include microprocessors, networking,communication, and field-programmable logic devices. The integratedcircuit device 90 may also comprise of circuitry to determine if memoryarray 80 (or a segment of memory array 80, for example when the segmentincludes at least 0.1% of the memory cells) has been idle for a periodof time, which may trigger a shadowing operation to conserve powerconsumption of the memory array 80 and subsequently the integratedcircuit device 90. The integrated circuit device 90 may also comprise ofa timer circuitry to ascertain that the elapsed idle time is greaterthan an elapsed time threshold, for example thirty seconds.

FIGS. 46B and 46C illustrate examples of memory arrays 80 and 81 formedby a plurality of memory cells 150. The memory array 81 shown in FIG.46C comprises of links of a plurality memory cells 150 connected inparallel, for example as described in U.S. application Ser. No.12/897,528 “Compact Semiconductor Memory Device Having Reduced Number ofContacts, Methods of Operating and Methods of Making” (“Widjaja-6”),which is hereby incorporated herein, in its entirety, by referencethereto. For simplicity, only memory array 80 will be shown from hereon.

Memory cell 150 has both volatile and non-volatile functionality similarto memory cell 50. A flowchart 100 describing the operation of memorycell 150 is shown in FIG. 1.

When power is applied to memory cell 150, memory cell 150 stores itsstates in floating body region 24 and may operate like a capacitorlessmemory cell 35. In one embodiment, the non-volatile memory element isinitialized to have a low resistivity state.

Several operations may be performed on memory cell 150 during thevolatile operation, such as holding, read, write logic-1, and writelogic-0 operations, following the principles of the operation of memorycell 35.

When power down is detected, e.g., when a user turns off the power tocell 150, or the power is inadvertently interrupted, or for any otherreason, power is at least temporarily discontinued to cell 150, datastored in the floating body region 24 is transferred to the resistancechange memory 40. This operation is referred to as “shadowing” and isdescribed with reference to FIGS. 47 and 48.

To perform a shadowing operation, a positive voltage is applied to thesubstrate terminal 78, zero voltage is applied to the SL terminal 72,zero voltage is applied to the BL terminal 74, and zero voltage isapplied to the WL terminal 70. The positive voltage applied to thesubstrate terminal 78 during shadowing operation is greater than thepositive voltage applied to the substrate terminal 78 during holdingoperation. When the memory cell 150 is in a volatile logic-1 state (i.e.having a positively charged floating body 24), the SCR device 30 b willbe turned on. The positive voltage applied to the substrate terminal 78is controlled such that the electrical current flowing through theresistance change memory 40 is sufficient to change the resistivity ofthe materials from a low resistivity state to a high resistivity state.For phase change materials, the crystalline state changes from acrystalline phase to an amorphous phase, while in metal oxide systems,this may involve the rupture of conductive filaments. Accordingly, thenon-volatile resistance change material element 40 will be in a highresistivity state when the volatile memory of cell 150 is in a logic-1state.

When the floating body 24 is neutral or only slightly positive (forexample, when the potential of the floating body region is less than0.3V), the SCR device 30 b will be turned off. Therefore, no (or low)electrical current flows through the resistance change memory element 40and it will retain its low resistivity state. Accordingly, thenon-volatile resistance change memory element 40 will be in a lowresistivity state when the volatile memory of cell 150 is in a logic-0state.

In one particular non-limiting example of this embodiment, about +2.0volts is applied to the substrate terminal 78, about 0.0 volts isapplied to the WL terminal 70, BL terminal 74, and SL terminal 72 sothat about 700 μA current flows between substrate terminal 78 and SLterminal 72.

Note that this process occurs non-algorithmically, as the state of thefloating body 24 does not have to be read, interpreted, or otherwisemeasured to determine what state to write the non-volatile resistancechange memory 40 to. Rather, the shadowing process occurs automatically,driven by electric potential differences. Accordingly, this process isorders of magnitude faster than one that requires algorithmicintervention. In addition, no control circuitry, such as a memorycontroller, is required between the volatile memory component and thenon-volatile memory component, allowing for a close proximity betweenthe floating body transistor 20 and the resistance change element 40, asshown in FIGS. 43 and 44A.

When power is restored to cell 150, the state of the cell 150 as storedon the non-volatile resistance change memory 40 is restored intofloating body region 24. The restore operation (data restoration fromnon-volatile memory to volatile memory) is described with reference toFIGS. 49 and 50. In one embodiment, to perform the restore operation, anegative voltage is applied to the WL terminal 70, a positive voltage isapplied to the BL terminal 74, a negative voltage is applied to the SLterminal 72, and zero or a positive voltage is applied to the substrateterminal 78.

These conditions will result in band-to-band tunneling hole injectioninto the floating body 24. However, if the resistance change memory isin a low resistivity state, the negative voltage applied to the SLterminal 72 will evacuate holes in the floating body 24 because the p-njunction formed by the floating body 24 and the source line region 16 isforward-biased. Consequently, the volatile memory state of memory cell150 will be restored to a logic-0 state upon completion of the restoreoperation, restoring the state that the memory cell 150 held prior tothe shadowing operation.

If the resistance change memory 40 is in a high resistivity state, alarger voltage drop will develop across the resistance change memory 40and no (or low) current flows through the resistance change memory 40,hence the holes accumulated in the floating body 24 will not beevacuated. As a result, the memory logic-1 state that the memory cell150 held prior to the shadowing operation will be restored.

In one particular non-limiting example of this embodiment, about −1.2volts is applied to the SL terminal 72, about +1.2 volts is applied toBL terminal 74, about −1.2 volts is applied to WL terminal 70, about 0.0volts or +1.2 volts is applied to the substrate terminal 78. However,these voltage levels may vary, while maintaining the relativerelationships between the charges applied, as described above.

Note that this process occurs non-algorithmically, as the state of thenon-volatile resistance change memory 40 does not have to be read,interpreted, or otherwise measured to determine what state to restorethe floating body 24 to. Rather, the restoration process occursautomatically, driven by resistivity state differences. Accordingly,this process is orders of magnitude faster than one that requiresalgorithmic intervention. In addition, no control circuitry, such as amemory controller, is required between the volatile memory component andthe non-volatile memory component, allowing for a close proximitybetween the floating body transistor 20 and the resistance changeelement 40, as shown in FIGS. 43 and 44A.

After restoring the memory cell(s) 150, the resistance changememory(ies) 40 is/are reset to a predetermined state, e.g., a lowresistivity state, so that each resistance change memory 40 has a knownstate prior to performing another shadowing operation.

FIGS. 51 and 52 illustrate a reset operation performed on a memory array80 and a memory cell 150, respectively. To perform a reset operation, apositive voltage is applied to the substrate terminal 78, zero voltageis applied to the SL terminal 72, zero voltage is applied to the BLterminal 74, and zero voltage is applied to the WL terminal 70. Thepositive voltage applied to the substrate terminal 78 during resetoperation is greater than the positive voltage applied to the substrateterminal 78 during holding operation and the resulting current thatflows from the substrate terminal 78 to the SL terminal 72 may be lessthan the current flowing during shadowing operation. When the memorycell 150 is in a volatile logic-1 state (i.e. having a positivelycharged floating body 24), the SCR device 30 b will be turned on. Thepositive voltage applied to the substrate terminal 78 is controlled suchthat the electrical current flowing through the resistance change memory40 is sufficient to change the resistivity of the materials from a highresistivity state to a low resistivity state. For phase changematerials, the crystalline state changes from an amorphous phase to acrystalline phase, while in metal oxide systems, this may involve theformation of conductive filaments. Accordingly, the non-volatileresistance change material element 40 will be in a low resistivity statewhen the volatile memory of cell 150 is in a logic-1 state.

When the floating body 24 is neutral or only slightly positive (forexample, when the potential of the floating body region is less than0.3V), the SCR device 30 b will be turned off. Therefore, no (or low)electrical current flows through the resistance change memory element 40and it will retain its low resistivity state. Accordingly, thenon-volatile resistance change memory element 40 will be in a lowresistivity state when the volatile memory of cell 150 is in a logic-0state.

In one particular non-limiting example of this embodiment, about +1.5volts is applied to the substrate terminal 78, about 0.0 volts isapplied to the WL terminal 70, BL terminal 74, and SL terminal 72 sothat about 400 μA current flows between substrate terminal 78 and SLterminal 72.

Memory cell 150 may alternatively be fabricated on asilicon-on-insulator (SOI) substrate 13 as illustrated in FIG. 53, wherea buried insulator 23, an illustrative, non-exclusive example of whichincludes a buried oxide layer, bounds the substrate 12 at the bottom.

In addition, memory cell 150 may alternatively comprise athree-dimensional structure as shown in FIGS. 54A and 54B, where thememory cell 150 comprise a fin structure 52, extending substantiallyperpendicular to, and above the top surface of the substrate 12/buriedinsulator 23.

In another alternative embodiment, memory cell 150 may be insulated fromneighboring memory cells 150 by an insulating layer 26 and a shallowerinsulating layer 28, as shown in FIG. 55, where the shallower insulatinglayer 28 is shown in dashed lines. The shallower insulating layer 28insulates the floating body region 24, but allows the buried layer 22 tobe continuous in the perpendicular direction of the cross-sectional viewshown in FIG. 55. Since the buried layer 22 of memory cells 150 iscontinuous in one direction, but is insulated in the other perpendiculardirection (by the insulating layer 26), buried layer 22 may be connectedto a terminal or an addressable line and used in memory cell accessselection and define a row (or column) direction. Memory cell 150 maythen operate in volatile mode independent of the resistivity state ofthe resistance change memory 40. The volatile mode operation of memorycell 150 will be similar to the half-transistor floating body memorycell, defined by the gate 60, bit line region 18, buried well region 22,as described for example in U.S. application Ser. No. 12/897,538, “ASemiconductor Memory Device Having an Electrically Floating BodyTransistor” (“Widjaja-4”), and in U.S. application Ser. No. 12/897,516,“A Semiconductor Memory Device Having an Electrically Floating BodyTransistor” (“Widjaja-5), both of which are hereby incorporated herein,in their entireties, by reference thereto.

In another alternative embodiment, the initial state of the resistancechange memory element 40 may be in a high resistivity state. In thisembodiment, due to the a high resistance memory element 40 electricallyconnected to the SL terminal 72, the volatile operation of memory cell150 may employ the silicon controlled rectifier (SCR) principle asdescribed, for example, in Widjaja-2. The volatile operation of memorycell 150 will utilize WL terminal 70, BL terminal 74, and substrateterminal 78. Alternatively, the volatile mode operation of memory cell150 will be similar to the half-transistor floating body memory cell,defined by the gate 60, bit line region 18, buried well region 22, asdescribed for example in U.S. application Ser. No. 12/897,538, “ASemiconductor Memory Device Having an Electrically Floating BodyTransistor” (“Widjaja-4”), and in U.S. application Ser. No. 12/897,516,“A Semiconductor Memory Device Having an Electrically Floating BodyTransistor” (“Widjaja-5), which are hereby incorporated herein, in theirentireties, by reference thereto.

To perform a shadowing operation, a positive voltage is applied to thesubstrate terminal 78, zero voltage is applied to the SL terminal 72,zero voltage is applied to the BL terminal 74, and zero voltage isapplied to the WL terminal 70. The positive voltage applied to thesubstrate terminal 78 during a shadowing operation is greater than thepositive voltage applied to the substrate terminal 78 during a holdingoperation. When the memory cell 150 is in a volatile logic-1 state (i.e.having a positively charged floating body 24), the SCR device 30 b willbe turned on. The positive voltage applied to the substrate terminal 78is controlled such that the electrical current flowing through theresistance change memory 40 is sufficient to change the resistivity ofthe materials from a high resistivity state to a low resistivity state.For phase change materials, the crystalline state changes from anamorphous phase to a crystalline phase, while in metal oxide systems,this may involve the formation of conductive filaments. Accordingly, thenon-volatile resistance change material element 40 will be in a lowresistivity state when the volatile memory of cell 150 is in a logic-1state.

When the floating body 24 is neutral or only slightly positive (forexample, when the potential of the floating body region is less than0.3V), the SCR device 30 b will be turned off. Therefore, no (or low)electrical current flows through the resistance change memory element 40and it will retain its high resistivity state. Accordingly, thenon-volatile resistance change memory element 40 will be in a highresistivity state when the volatile memory of cell 150 is in a logic-0state.

In one particular non-limiting example of this embodiment, about +1.5volts is applied to the substrate terminal 78, about 0.0 volts isapplied to the WL terminal 70, BL terminal 74, and SL terminal 72 sothat about 400 μA current flows between substrate terminal 78 and SLterminal 72.

Note that this process occurs non-algorithmically, as the state of thefloating body 24 does not have to be read, interpreted, or otherwisemeasured to determine what state to write the non-volatile resistancechange memory 40 to. Rather, the shadowing process occurs automatically,driven by electrical potential differences. Accordingly, this process isorders of magnitude faster than one that requires algorithmicintervention.

A restore operation may be performed using a band-to-band tunnelingoperation by applying the following bias condition: a negative voltageis applied to the WL terminal 70, a positive voltage is applied to theSL terminal 72, zero voltage is applied to the BL terminal 74, zero orpositive voltage is applied to the substrate terminal 78.

If resistance change memory element 40 is in a low resistivity state,these conditions will result in result in band-to-band tunneling holeinjection into the floating body 24. However, if the resistance changememory is in a high resistivity state, the SL terminal 72 may act as anopen circuit, and as a result, the electric field in the source lineregion 16 near the gate 60 is not sufficient to generate holes throughband-to-band tunneling mechanism.

In one particular non-limiting example of this embodiment, about −1.2volts is applied to the WL terminal 70, about +1.2 volts is applied toSL terminal 72, about 0.0 volts is applied to BL terminal 74, about 0.0volts or +1.2 volts is applied to substrate terminal 78.

Note that this process occurs non-algorithmically, as the state of thefloating body 24 does not have to be read, interpreted, or otherwisemeasured to determine what state to write the non-volatile resistancechange memory 40 to. Rather, the restore process occurs automatically,driven by electrical potential differences. Accordingly, this process isorders of magnitude faster than one that requires algorithmicintervention.

To perform a reset operation, a positive voltage is applied to thesubstrate terminal 78, zero voltage is applied to the SL terminal 72,zero voltage is applied to the BL terminal 74, and zero voltage isapplied to the WL terminal 70. The positive voltage applied to thesubstrate terminal 78 during reset operation is greater than thepositive voltage applied to the substrate terminal 78 during holding aoperation and the resulting current that flows from the substrateterminal 78 to the SL terminal 72 may be greater than the currentflowing during a shadowing operation. When the memory cell 150 is in avolatile logic-1 state (i.e. having a positively charged floating body24), the SCR device 30 b will be turned on. The positive voltage appliedto the substrate terminal 78 is controlled such that the electricalcurrent flowing through the resistance change memory 40 is sufficient tochange the resistivity of the materials from a low resistivity state toa high resistivity state. For phase change materials, the crystallinestate changes from a crystalline phase to an amorphous phase, while inmetal oxide systems, this may involve the rupture of conductivefilaments. Accordingly, the non-volatile resistance change materialelement 40 will be in a high resistivity state when the volatile memoryof cell 150 is in a logic-1 state.

When the floating body 24 is neutral or only slightly positive (forexample, when the potential of the floating body region is less than0.3V), the SCR device 30 b will be turned off. Therefore, no electriccurrent flows through the resistance change memory element 40 and itwill retain its high resistivity state. Accordingly, the non-volatileresistance change memory element 40 will be in a high resistivity statewhen the volatile memory of cell 150 is in a logic-0 state.

In one particular non-limiting example of this embodiment, about +2.0volts is applied to the substrate terminal 78, about 0.0 volts isapplied to the WL terminal 70, BL terminal 74, and SL terminal 72 sothat about 700 μA current flows between substrate terminal 78 and SLterminal 72.

Note that this process occurs non-algorithmically, as the state of thefloating body 24 does not have to be read, interpreted, or otherwisemeasured to determine what state to write the non-volatile resistancechange memory 40 to. Rather, the shadowing process occurs automatically,driven by electrical potential differences. Accordingly, this process isorders of magnitude faster than one that requires algorithmicintervention.

The integrated circuit device 90 may also comprise of a counter circuit82, which may determine if a memory cell 150 (or a group of memory cells150, the group may comprise of for example a row of memory cells 150 ora few rows of memory cells 150) is in volatile mode operation and hasnot been accessed for a certain period of time, for example, one second,although another predetermined time period may be used alternatively.Once the memory cell 150 is idle for greater than an elapsed timethreshold (i.e., predetermined time period), the memory cell 150 (or agroup of memory cells 150) may be put into the non-volatile statethrough the shadowing operation. Since memory cell 150 does not requirepower to maintain its states, this operation may allow for a loweroperating power of the integrated circuit device 90.

Memory cells 50 and 150 can also be configured to store only volatiledata or only non-volatile data (where the non-volatile data is notdetermined by the state of the volatile memory) in addition to havingboth volatile and non-volatile functionality as has been described.Thus, memory array 80 or 81 may comprise segments of memory cells 50 or150 configured to store only volatile data and segments of memory cells50 or 150 configured to store only non-volatile data, for example asdescribed in “Resistive-Memory Embedded Unified RAM (R-URAM)”, S. Kim etal., pp. 2670-2674, IEEE Transactions on Electron Devices, vol. 56, no.11, December 2009, which is hereby incorporated herein, in its entirety,by reference thereto, where a unipolar resistive memory element Al₂O₃ isconnected to the gate of a capacitorless DRAM. In embodiments wheresegments of memory cells 50 or 150 configured to store only volatiledata or only non-volatile data, array 80 or 81 may or may not furtherinclude one or more segments of memory cells configured to storevolatile memory and non-volatile memory in a manner as described.

From the foregoing it can be seen that with the present invention, asemiconductor memory with both volatile and non-volatile functionalityis achieved. While the foregoing written description of the inventionenables one of ordinary skill to make and use what is consideredpresently to be the best mode thereof, those of ordinary skill willunderstand and appreciate the existence of variations, combinations, andequivalents of the specific embodiment, method, and examples herein. Theinvention should therefore not be limited by the above describedembodiment, method, and examples, but by all embodiments and methodswithin the scope and spirit of the invention as claimed.

While the present invention has been described with reference to thespecific embodiments thereof, it should be understood by those skilledin the art that various changes may be made and equivalents may besubstituted without departing from the true spirit and scope of theinvention. In addition, many modifications may be made to adapt aparticular situation, material, composition of matter, process, processstep or steps, to the objective, spirit and scope of the presentinvention. All such modifications are intended to be within the scope ofthe claims appended hereto.

That which is claimed is:
 1. A semiconductor memory cell comprising: acapacitorless transistor having a floating body configured to store dataas charge therein when power is applied to said cell; and a non-volatilememory comprising a bipolar resistive change element; wherein saidfloating body has a first conductivity type selected from n-typeconductivity type and p-type conductivity type; said memory cell furthercomprising first and second regions at first and second locations ofsaid cell, said first and second regions each having a secondconductivity type selected from said n-type conductivity type and saidp-type conductivity type and being different from said firstconductivity type.
 2. The semiconductor memory cell of claim 1, whereinsaid bipolar resistive change element is configured to store said datastored in said floating body upon transfer thereto.
 3. The semiconductormemory cell of claim 1, wherein said bipolar resistive change elementcomprises a material selected from at least one of: transition metaloxide materials, ferroelectric materials and ferromagnetic materials. 4.The semiconductor memory cell of claim 1, wherein said bipolar resistivechange element is electrically connected to said capacitorlesstransistor and a distance between said bipolar resistive change elementand said capacitorless transistor, when electrically connected, is inthe range from about 90 nm to 1 μm.
 5. The semiconductor memory cell ofclaim 1, wherein said bipolar resistive change element comprises anelectrode and a bipolar resistive change material electrically connectedto one of said first and second regions.
 6. The semiconductor memorycell of claim 5, wherein said bipolar resistive change element iselectrically connected to said one of said first and second regions viaa conductive element.
 7. The semiconductor memory cell of claim 5,further comprising an addressable line electrically connected to saidbipolar resistive change element.
 8. The semiconductor memory cell ofclaim 7, wherein said bipolar resistive change element further comprisesa conductive material element interconnecting said addressable line andsaid bipolar resistive change material.
 9. The semiconductor memory cellof claim 1, further comprising: a substrate being made of a materialhaving said second conductivity type; and a buried layer in saidsubstrate below said first and second regions, spaced apart from saidfirst and second regions and having said second conductivity type;wherein said floating body is formed between said first and secondregions and said buried layer; and wherein said non-volatile memory iselectrically connected to one of said first and second regions.
 10. Thesemiconductor memory cell of claim 1, further comprising: a substratebeing made of a material having said second conductivity type; a well insaid substrate, said well having said first conductivity type; and aburied layer located between said well and said first and secondregions, spaced apart from said first and second regions and having saidsecond conductivity type; wherein said floating body is formed betweensaid first and second regions and said buried layer; and wherein saidnon-volatile memory is electrically connected to one of said first andsecond regions.
 11. The semiconductor memory cell of claim 10, whereinsaid substrate is a well formed in a second substrate.
 12. Thesemiconductor memory cell of claim 1, wherein said cell has athree-dimensional structure comprising a fin structure extendingsubstantially perpendicular to, and above a top surface of a substrate.13. A semiconductor memory array comprising a plurality of semiconductormemory cells as recited in claim 1, arranged in a matrix of at least onerow and at least one column.
 14. An integrated circuit device comprisingthe semiconductor memory array of claim 13 and circuitry configured todetermine whether said semiconductor array, or a portion of saidsemiconductor memory array, has been idle for a time period equal to orgreater than a predetermined time period.
 15. The semiconductor memorycell of claim 1, wherein said floating body comprises a bipolar memorydevice.
 16. A semiconductor memory cell comprising: a silicon controlledrectifier device configured to store data and operate as volatile memorywhen power is applied to said cell; and a non-volatile memory comprisinga bipolar resistance change element: wherein said silicon controlledrectifier device comprises a floating body region having a firstconductivity type selected from n-type conductivity type and p-typeconductivity type; said memory cell further comprising first and secondregions at first and second locations of said cell, said first andsecond regions each having a second conductivity type selected from saidn-type conductivity type and said p-type conductivity type and beingdifferent from said first conductivity type.
 17. A method of operatingsemiconductor memory to function as volatile memory, while having theability to retain stored data when power is discontinued to thesemiconductor memory, said method comprising: storing data in acapacitorless transistor having a floating body configured to store dataas charge therein when power is applied to said memory, wherein saidfloating body operates as a capacitorless DRAM cell or a bi-stable SRAMcell; and storing data in a bipolar resistance change element byconfiguring the bipolar resistance change element in one of a lowresistivity state or a high resistivity state, wherein each of saidresistivity states corresponds to a different data value, respectively.18. The method of claim 17, further comprising: restoring said data fromsaid bipolar non-volatile memory to said floating body as volatilememory.
 19. The method of claim 18, wherein said restoring comprisesevacuating holes from the volatile memory when the bipolar non-volatilememory is in a low resistance state, but maintaining a presentlyexisting charge in the volatile memory when the bipolar non-volatilememory is in a high resistance state.
 20. The method of claim 18,wherein said restoring and said maintaining are performednon-algorithmically.